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Doc: update the rest of section 9.4 for new function table layout.
Notably, this replaces the previous handwaving about these functions' behavior with "character"-type inputs with some actual facts.
This commit is contained in:
Tom Lane
parent
0cacb2b79d
commit
9aece5cd05
@ -2030,10 +2030,12 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
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This section describes functions and operators for examining and
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manipulating string values. Strings in this context include values
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of the types <type>character</type>, <type>character varying</type>,
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and <type>text</type>. Unless otherwise noted, all
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of the functions listed below work on all of these types, but be
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wary of potential effects of automatic space-padding when using the
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<type>character</type> type.
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and <type>text</type>. Except where noted, these functions and operators
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are declared to accept and return type <type>text</type>. They will
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interchangeably accept <type>character varying</type> arguments.
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Values of type <type>character</type> will be converted
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to <type>text</type> before the function or operator is applied, resulting
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in stripping any trailing spaces in the <type>character</type> value.
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</para>
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<para>
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@ -2062,96 +2064,94 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
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<table id="functions-string-sql">
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<title><acronym>SQL</acronym> String Functions and Operators</title>
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<tgroup cols="5">
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<tgroup cols="1">
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<thead>
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<row>
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<entry>Function</entry>
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<entry>Return Type</entry>
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<entry>Description</entry>
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<entry>Example</entry>
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<entry>Result</entry>
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<entry role="functableentry">
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Function/Operator<?br?>Description<?br?>Example(s)
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</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><literal><parameter>string</parameter> <literal>||</literal>
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<parameter>string</parameter></literal></entry>
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<entry> <type>text</type> </entry>
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<entry>
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String concatenation
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<entry role="functableentry">
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<indexterm>
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<primary>character string</primary>
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<secondary>concatenation</secondary>
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</indexterm>
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<type>text</type> <literal>||</literal> <type>text</type>
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<returnvalue>text</returnvalue>
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<?br?>
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Concatenates the two strings.
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<?br?>
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<literal>'Post' || 'greSQL'</literal>
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<returnvalue>PostgreSQL</returnvalue>
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</entry>
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<entry><literal>'Post' || 'greSQL'</literal></entry>
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<entry><literal>PostgreSQL</literal></entry>
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</row>
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<row>
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<entry>
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<literal><parameter>string</parameter> <literal>||</literal>
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<parameter>non-string</parameter></literal>
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or
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<literal><parameter>non-string</parameter> <literal>||</literal>
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<parameter>string</parameter></literal>
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<entry role="functableentry">
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<type>text</type> <literal>||</literal> <type>anynonarray</type>
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or <type>anynonarray</type> <literal>||</literal> <type>text</type>
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<returnvalue>text</returnvalue>
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<?br?>
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Converts the non-string input to text, then concatenates the two
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strings. (The non-string input cannot be of an array type, because
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that would create ambiguity with the array <literal>||</literal>
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operators. If you want to concatenate an array's text equivalent,
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cast it to <type>text</type> explicitly.)
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<?br?>
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<literal>'Value: ' || 42</literal>
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<returnvalue>Value: 42</returnvalue>
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</entry>
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<entry> <type>text</type> </entry>
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<entry>
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String concatenation with one non-string input
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</entry>
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<entry><literal>'Value: ' || 42</literal></entry>
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<entry><literal>Value: 42</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>normalized</primary>
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</indexterm>
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<indexterm>
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<primary>Unicode normalization</primary>
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</indexterm>
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<literal><parameter>string</parameter> is <optional>not</optional> <optional><parameter>form</parameter></optional> normalized</literal>
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</entry>
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<entry><type>boolean</type></entry>
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<entry>
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<type>text</type> <literal>IS</literal> <optional><literal>NOT</literal></optional> <optional><parameter>form</parameter></optional> <literal>NORMALIZED</literal>
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<returnvalue>boolean</returnvalue>
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<?br?>
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Checks whether the string is in the specified Unicode normalization
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form. The optional parameter specifies the form:
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<literal>NFC</literal> (default), <literal>NFD</literal>,
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<literal>NFKC</literal>, <literal>NFKD</literal>. This expression can
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only be used if the server encoding is <literal>UTF8</literal>. Note
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form. The optional <parameter>form</parameter> key word specifies the
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form: <literal>NFC</literal> (the default), <literal>NFD</literal>,
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<literal>NFKC</literal>, or <literal>NFKD</literal>. This expression can
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only be used when the server encoding is <literal>UTF8</literal>. Note
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that checking for normalization using this expression is often faster
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than normalizing possibly already normalized strings.
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<?br?>
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<literal>U&'\0061\0308bc' IS NFD NORMALIZED</literal>
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<returnvalue>t</returnvalue>
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</entry>
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<entry><literal>U&'\0061\0308bc' IS NFD NORMALIZED</literal></entry>
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<entry><literal>true</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>bit_length</primary>
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</indexterm>
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<literal><function>bit_length(<parameter>string</parameter>)</function></literal>
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<function>bit_length</function> ( <type>text</type> )
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<returnvalue>integer</returnvalue>
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<?br?>
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Returns number of bits in the string (8
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times the <function>octet_length</function>).
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<?br?>
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<literal>bit_length('jose')</literal>
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<returnvalue>32</returnvalue>
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</entry>
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<entry><type>int</type></entry>
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<entry>Number of bits in string</entry>
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<entry><literal>bit_length('jose')</literal></entry>
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<entry><literal>32</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>char_length</primary>
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</indexterm>
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<literal><function>char_length(<parameter>string</parameter>)</function></literal> or <literal><function>character_length(<parameter>string</parameter>)</function></literal>
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</entry>
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<entry><type>int</type></entry>
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<entry>
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Number of characters in string
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<indexterm>
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<primary>character string</primary>
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<secondary>length</secondary>
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@ -2161,175 +2161,224 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
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<secondary sortas="character string">of a character string</secondary>
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<see>character string, length</see>
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</indexterm>
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<function>char_length</function> ( <type>text</type> )
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or <function>character_length</function> ( <type>text</type> )
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<returnvalue>integer</returnvalue>
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<?br?>
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Returns number of characters in the string.
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<?br?>
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<literal>char_length('josé')</literal>
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<returnvalue>4</returnvalue>
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</entry>
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<entry><literal>char_length('jose')</literal></entry>
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<entry><literal>4</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>lower</primary>
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</indexterm>
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<literal><function>lower(<parameter>string</parameter>)</function></literal>
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<function>lower</function> ( <type>text</type> )
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<returnvalue>text</returnvalue>
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<?br?>
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Converts the string to all lower case, according to the rules of the
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database's locale.
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<?br?>
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<literal>lower('TOM')</literal>
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<returnvalue>tom</returnvalue>
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</entry>
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<entry><type>text</type></entry>
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<entry>Convert string to lower case</entry>
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<entry><literal>lower('TOM')</literal></entry>
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<entry><literal>tom</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>normalize</primary>
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</indexterm>
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<indexterm>
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<primary>Unicode normalization</primary>
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</indexterm>
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<literal><function>normalize(<parameter>string</parameter> <type>text</type>
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<optional>, <parameter>form</parameter> </optional>)</function></literal>
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<function>normalize</function> ( <type>text</type>
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<optional>, <parameter>form</parameter> </optional> )
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<returnvalue>text</returnvalue>
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<?br?>
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Converts the string to the specified Unicode
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normalization form. The optional <parameter>form</parameter> key word
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specifies the form: <literal>NFC</literal> (the default),
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<literal>NFD</literal>, <literal>NFKC</literal>, or
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<literal>NFKD</literal>. This function can only be used when the
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server encoding is <literal>UTF8</literal>.
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<?br?>
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<literal>normalize(U&'\0061\0308bc', NFC)</literal>
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<returnvalue>U&'\00E4bc'</returnvalue>
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</entry>
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<entry><type>text</type></entry>
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<entry>
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Converts the string in the first argument to the specified Unicode
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normalization form. The optional second argument specifies the form
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as an identifier: <literal>NFC</literal> (default),
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<literal>NFD</literal>, <literal>NFKC</literal>,
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<literal>NFKD</literal>. This function can only be used if the server
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encoding is <literal>UTF8</literal>.
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</entry>
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<entry><literal>normalize(U&'\0061\0308bc', NFC)</literal></entry>
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<entry><literal>U&'\00E4bc'</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>octet_length</primary>
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</indexterm>
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<literal><function>octet_length(<parameter>string</parameter>)</function></literal>
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<function>octet_length</function> ( <type>text</type> )
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<returnvalue>integer</returnvalue>
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<?br?>
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Returns number of bytes in the string.
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<?br?>
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<literal>octet_length('josé')</literal>
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<returnvalue>5</returnvalue> (if server encoding is UTF8)
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</entry>
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<entry><type>int</type></entry>
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<entry>Number of bytes in string</entry>
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<entry><literal>octet_length('jose')</literal></entry>
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<entry><literal>4</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>octet_length</primary>
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</indexterm>
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<function>octet_length</function> ( <type>character</type> )
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<returnvalue>integer</returnvalue>
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<?br?>
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Returns number of bytes in the string. Since this version of the
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function accepts type <type>character</type> directly, it will not
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strip trailing spaces.
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<?br?>
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<literal>octet_length('abc '::character(4))</literal>
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<returnvalue>4</returnvalue>
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</entry>
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</row>
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<row>
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<entry role="functableentry">
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<indexterm>
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<primary>overlay</primary>
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</indexterm>
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<literal><function>overlay(<parameter>string</parameter> placing <parameter>string</parameter> from <type>int</type> <optional>for <type>int</type></optional>)</function></literal>
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<function>overlay</function> ( <parameter>string</parameter> <type>text</type> <literal>PLACING</literal> <parameter>newsubstring</parameter> <type>text</type> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
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<returnvalue>text</returnvalue>
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<?br?>
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Replaces the substring of <parameter>string</parameter> that starts at
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the <parameter>start</parameter>'th character and extends
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for <parameter>count</parameter> characters
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with <parameter>newsubstring</parameter>.
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If <parameter>count</parameter> is omitted, it defaults to the length
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of <parameter>newsubstring</parameter>.
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<?br?>
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<literal>overlay('Txxxxas' placing 'hom' from 2 for 4)</literal>
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<returnvalue>Thomas</returnvalue>
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</entry>
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<entry><type>text</type></entry>
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<entry>
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Replace substring
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</entry>
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<entry><literal>overlay('Txxxxas' placing 'hom' from 2 for 4)</literal></entry>
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<entry><literal>Thomas</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>position</primary>
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</indexterm>
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<literal><function>position(<parameter>substring</parameter> in <parameter>string</parameter>)</function></literal>
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<function>position</function> ( <parameter>substring</parameter> <type>text</type> <literal>IN</literal> <parameter>string</parameter> <type>text</type> )
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<returnvalue>integer</returnvalue>
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<?br?>
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Returns starting index of specified <parameter>substring</parameter>
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within <parameter>string</parameter>, or zero if it's not present.
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<?br?>
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<literal>position('om' in 'Thomas')</literal>
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<returnvalue>3</returnvalue>
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</entry>
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<entry><type>int</type></entry>
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<entry>Location of specified substring</entry>
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<entry><literal>position('om' in 'Thomas')</literal></entry>
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<entry><literal>3</literal></entry>
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</row>
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<row>
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<entry>
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<entry role="functableentry">
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<indexterm>
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<primary>substring</primary>
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</indexterm>
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<literal><function>substring(<parameter>string</parameter> <optional>from <type>int</type></optional> <optional>for <type>int</type></optional>)</function></literal>
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<function>substring</function> ( <parameter>string</parameter> <type>text</type> <optional> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> </optional> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
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<returnvalue>text</returnvalue>
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<?br?>
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Extracts the substring of <parameter>string</parameter> starting at
|
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the <parameter>start</parameter>'th character if that is specified,
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and stopping after <parameter>count</parameter> characters if that is
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specified. Provide at least one of <parameter>start</parameter>
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and <parameter>count</parameter>.
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<?br?>
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<literal>substring('Thomas' from 2 for 3)</literal>
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<returnvalue>hom</returnvalue>
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<?br?>
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<literal>substring('Thomas' from 3)</literal>
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<returnvalue>omas</returnvalue>
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<?br?>
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<literal>substring('Thomas' for 2)</literal>
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<returnvalue>Th</returnvalue>
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</entry>
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<entry><type>text</type></entry>
|
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<entry>
|
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Extract substring (provide at least one of <literal>from</literal>
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and <literal>for</literal>)
|
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</entry>
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<entry><literal>substring('Thomas' from 2 for 3)</literal></entry>
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<entry><literal>hom</literal></entry>
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</row>
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<row>
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<entry><literal><function>substring(<parameter>string</parameter> from <replaceable>pattern</replaceable>)</function></literal></entry>
|
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<entry><type>text</type></entry>
|
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<entry>
|
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Extract substring matching POSIX regular expression (see
|
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<xref linkend="functions-matching"/> for more information on pattern
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matching)
|
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<entry role="functableentry">
|
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<function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>FROM</literal> <replaceable>pattern</replaceable> <type>text</type> )
|
||||
<returnvalue>text</returnvalue>
|
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<?br?>
|
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Extracts substring matching POSIX regular expression; see
|
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<xref linkend="functions-posix-regexp"/>.
|
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<?br?>
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<literal>substring('Thomas' from '...$')</literal>
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<returnvalue>mas</returnvalue>
|
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</entry>
|
||||
<entry><literal>substring('Thomas' from '...$')</literal></entry>
|
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<entry><literal>mas</literal></entry>
|
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</row>
|
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|
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<row>
|
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<entry><literal><function>substring(<parameter>string</parameter> from <replaceable>pattern</replaceable> for <replaceable>escape</replaceable>)</function></literal></entry>
|
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<entry><type>text</type></entry>
|
||||
<entry>
|
||||
Extract substring matching <acronym>SQL</acronym> regular expression
|
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(see <xref linkend="functions-matching"/> for more information on
|
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pattern matching)
|
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<entry role="functableentry">
|
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<function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>FROM</literal> <replaceable>pattern</replaceable> <type>text</type> <literal>FOR</literal> <replaceable>escape</replaceable> <type>text</type> )
|
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<returnvalue>text</returnvalue>
|
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<?br?>
|
||||
Extracts substring matching <acronym>SQL</acronym> regular expression;
|
||||
see <xref linkend="functions-similarto-regexp"/>.
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<?br?>
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<literal>substring('Thomas' from '%#"o_a#"_' for '#')</literal>
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<returnvalue>oma</returnvalue>
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</entry>
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<entry><literal>substring('Thomas' from '%#"o_a#"_' for '#')</literal></entry>
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<entry><literal>oma</literal></entry>
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</row>
|
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|
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<row>
|
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<entry>
|
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<entry role="functableentry">
|
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<indexterm>
|
||||
<primary>trim</primary>
|
||||
</indexterm>
|
||||
<literal><function>trim(<optional>leading | trailing | both</optional>
|
||||
<optional><parameter>characters</parameter></optional> from
|
||||
<parameter>string</parameter>)</function></literal>
|
||||
</entry>
|
||||
<entry><type>text</type></entry>
|
||||
<entry>
|
||||
Remove the longest string containing only characters in
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||||
<function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional>
|
||||
<optional> <parameter>characters</parameter> <type>text</type> </optional> <literal>FROM</literal>
|
||||
<parameter>string</parameter> <type>text</type> )
|
||||
<returnvalue>text</returnvalue>
|
||||
<?br?>
|
||||
Removes the longest string containing only characters in
|
||||
<parameter>characters</parameter> (a space by default) from the
|
||||
start, end, or both ends (<literal>both</literal> is the default)
|
||||
of <parameter>string</parameter>
|
||||
start, end, or both ends (<literal>BOTH</literal> is the default)
|
||||
of <parameter>string</parameter>.
|
||||
<?br?>
|
||||
<literal>trim(both 'xyz' from 'yxTomxx')</literal>
|
||||
<returnvalue>Tom</returnvalue>
|
||||
</entry>
|
||||
<entry><literal>trim(both 'xyz' from 'yxTomxx')</literal></entry>
|
||||
<entry><literal>Tom</literal></entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry>
|
||||
<literal><function>trim(<optional>leading | trailing
|
||||
| both</optional> <optional>from</optional>
|
||||
<parameter>string</parameter> <optional>,
|
||||
<parameter>characters</parameter></optional>)</function></literal>
|
||||
<entry role="functableentry">
|
||||
<function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional> <optional> <literal>FROM</literal> </optional>
|
||||
<parameter>string</parameter> <type>text</type> <optional>,
|
||||
<parameter>characters</parameter> <type>text</type> </optional> )
|
||||
<returnvalue>text</returnvalue>
|
||||
<?br?>
|
||||
This is a non-standard syntax for <function>trim()</function>.
|
||||
<?br?>
|
||||
<literal>trim(both from 'yxTomxx', 'xyz')</literal>
|
||||
<returnvalue>Tom</returnvalue>
|
||||
</entry>
|
||||
<entry><type>text</type></entry>
|
||||
<entry>
|
||||
Non-standard syntax for <function>trim()</function>
|
||||
</entry>
|
||||
<entry><literal>trim(both from 'yxTomxx', 'xyz')</literal></entry>
|
||||
<entry><literal>Tom</literal></entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry>
|
||||
<entry role="functableentry">
|
||||
<indexterm>
|
||||
<primary>upper</primary>
|
||||
</indexterm>
|
||||
<literal><function>upper(<parameter>string</parameter>)</function></literal>
|
||||
<function>upper</function> ( <type>text</type> )
|
||||
<returnvalue>text</returnvalue>
|
||||
<?br?>
|
||||
Converts the string to all upper case, according to the rules of the
|
||||
database's locale.
|
||||
<?br?>
|
||||
<literal>upper('tom')</literal>
|
||||
<returnvalue>TOM</returnvalue>
|
||||
</entry>
|
||||
<entry><type>text</type></entry>
|
||||
<entry>Convert string to upper case</entry>
|
||||
<entry><literal>upper('tom')</literal></entry>
|
||||
<entry><literal>TOM</literal></entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
@ -2380,7 +2429,7 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
|
||||
<optional>, <parameter>characters</parameter> <type>text</type> </optional> )
|
||||
<returnvalue>text</returnvalue>
|
||||
<?br?>
|
||||
Removes the longest string consisting only of characters
|
||||
Removes the longest string containing only characters
|
||||
in <parameter>characters</parameter> (a space by default)
|
||||
from the start and end of <parameter>string</parameter>.
|
||||
<?br?>
|
||||
@ -2912,7 +2961,7 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
|
||||
<function>strpos</function> ( <parameter>string</parameter> <type>text</type>, <parameter>substring</parameter> <type>text</type> )
|
||||
<returnvalue>integer</returnvalue>
|
||||
<?br?>
|
||||
Returns location of specified <parameter>substring</parameter>
|
||||
Returns starting index of specified <parameter>substring</parameter>
|
||||
within <parameter>string</parameter>, or zero if it's not present.
|
||||
(Same as <literal>position(<parameter>substring</parameter> in
|
||||
<parameter>string</parameter>)</literal>, but note the reversed
|
||||
@ -2932,7 +2981,8 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
|
||||
<type></type> )
|
||||
<returnvalue>text</returnvalue>
|
||||
<?br?>
|
||||
Extracts substring starting at index <parameter>start</parameter>,
|
||||
Extracts the substring of <parameter>string</parameter> starting at
|
||||
the <parameter>start</parameter>'th character,
|
||||
and extending for <parameter>count</parameter> characters if that is
|
||||
specified. (Same
|
||||
as <literal>substring(<parameter>string</parameter>
|
||||
|
||||
Loading…
Reference in New Issue
Block a user