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docs: update PL/pgSQL docs about the use of := and =

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This commit is contained in:
Bruce Momjian 2014-01-16 16:40:17 -05:00
parent a472ae1e4e
commit 7e1955b861
2 changed files with 17 additions and 7 deletions
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17
doc/src/sgml/plpgsql.sgml
View File

@ -328,7 +328,7 @@ arow RECORD;
<para>
The general syntax of a variable declaration is:
<synopsis>
<replaceable>name</replaceable> <optional> CONSTANT </optional> <replaceable>type</replaceable> <optional> COLLATE <replaceable>collation_name</replaceable> </optional> <optional> NOT NULL </optional> <optional> { DEFAULT | := } <replaceable>expression</replaceable> </optional>;
<replaceable>name</replaceable> <optional> CONSTANT </optional> <replaceable>type</replaceable> <optional> COLLATE <replaceable>collation_name</replaceable> </optional> <optional> NOT NULL </optional> <optional> { DEFAULT | := | = } <replaceable>expression</replaceable> </optional>;
</synopsis>
The <literal>DEFAULT</> clause, if given, specifies the initial value assigned
to the variable when the block is entered. If the <literal>DEFAULT</> clause
@ -343,6 +343,8 @@ arow RECORD;
is specified, an assignment of a null value results in a run-time
error. All variables declared as <literal>NOT NULL</>
must have a nonnull default value specified.
Equals (<literal>=</>) can be used instead of PL/SQL-compliant
<literal>:=</>.
</para>
<para>
@ -866,7 +868,7 @@ PREPARE <replaceable>statement_name</>(integer, integer) AS SELECT $1 &lt; $2;
An assignment of a value to a <application>PL/pgSQL</application>
variable is written as:
<synopsis>
<replaceable>variable</replaceable> := <replaceable>expression</replaceable>;
<replaceable>variable</replaceable> { := | = } <replaceable>expression</replaceable>;
</synopsis>
As explained previously, the expression in such a statement is evaluated
by means of an SQL <command>SELECT</> command sent to the main
@ -874,7 +876,8 @@ PREPARE <replaceable>statement_name</>(integer, integer) AS SELECT $1 &lt; $2;
a row value, if the variable is a row or record variable). The target
variable can be a simple variable (optionally qualified with a block
name), a field of a row or record variable, or an element of an array
that is a simple variable or field.
that is a simple variable or field. Equals (<literal>=</>) can be
used instead of PL/SQL-compliant <literal>:=</>.
</para>
<para>
@ -1411,7 +1414,7 @@ EXECUTE format('UPDATE tbl SET %I = $1 WHERE key = $2', colname)
command, which has the form:
<synopsis>
GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable> = <replaceable>item</replaceable> <optional> , ... </optional>;
GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable> { = | := } <replaceable>item</replaceable> <optional> , ... </optional>;
</synopsis>
This command allows retrieval of system status indicators. Each
@ -1425,6 +1428,8 @@ GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceabl
<acronym>SQL</acronym> command. Note that <varname>RESULT_OID</>
is only useful after an <command>INSERT</command> command into a
table containing OIDs.
Equals (<literal>:=</>) can be used instead of SQL-standard
<literal>=</> for <command>GET DIAGNOSTICS</>.
</para>
<para>
@ -2672,7 +2677,7 @@ SELECT merge_db(1, 'dennis');
<command>GET STACKED DIAGNOSTICS</command> command, which has the form:
<synopsis>
GET STACKED DIAGNOSTICS <replaceable>variable</replaceable> = <replaceable>item</replaceable> <optional> , ... </optional>;
GET STACKED DIAGNOSTICS <replaceable>variable</replaceable> { = | := } <replaceable>item</replaceable> <optional> , ... </optional>;
</synopsis>
Each <replaceable>item</replaceable> is a key word identifying a status
@ -2776,7 +2781,7 @@ END;
<para>
<synopsis>
GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable> = <replaceable>PG_CONTEXT</replaceable> <optional> , ... </optional>;
GET <optional> CURRENT </optional> DIAGNOSTICS <replaceable>variable</replaceable> { = | := } <replaceable>PG_CONTEXT</replaceable> <optional> , ... </optional>;
</synopsis>

7
src/pl/plpgsql/src/pl_gram.y
View File

@ -796,7 +796,12 @@ decl_defkey : assign_operator
| K_DEFAULT
;
assign_operator : '=' /* not documented because it might be removed someday */
/*
* Ada-based PL/SQL uses := for assignment and variable defaults, while
* the SQL standard uses equals for these cases and for GET
* DIAGNOSTICS, so we support both. FOR and OPEN only support :=.
*/
assign_operator : '='
| COLON_EQUALS
;