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67 lines
2.1 KiB
Plaintext
67 lines
2.1 KiB
Plaintext
NOTE: Modified August 07, 2001 by Joe Conway. Updated for accuracy
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after combining soundex code into the fuzzystrmatch contrib
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---------------------------------------------------------------------
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The Soundex system is a method of matching similar sounding names
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(or any words) to the same code. It was initially used by the
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United States Census in 1880, 1900, and 1910, but it has little use
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beyond English names (or the English pronunciation of names), and
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it is not a linguistic tool.
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When comparing two soundex values to determine similarity, the
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difference function reports how close the match is on a scale
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from zero to four, with zero being no match and four being an
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exact match.
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The following are some usage examples:
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SELECT soundex('hello world!');
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SELECT soundex('Anne'), soundex('Ann'), difference('Anne', 'Ann');
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SELECT soundex('Anne'), soundex('Andrew'), difference('Anne', 'Andrew');
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SELECT soundex('Anne'), soundex('Margaret'), difference('Anne', 'Margaret');
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CREATE TABLE s (nm text);
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INSERT INTO s VALUES ('john');
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INSERT INTO s VALUES ('joan');
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INSERT INTO s VALUES ('wobbly');
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INSERT INTO s VALUES ('jack');
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SELECT * FROM s WHERE soundex(nm) = soundex('john');
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SELECT a.nm, b.nm FROM s a, s b WHERE soundex(a.nm) = soundex(b.nm) AND a.oid <> b.oid;
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CREATE FUNCTION text_sx_eq(text, text) RETURNS boolean AS
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'select soundex($1) = soundex($2)'
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LANGUAGE SQL;
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CREATE FUNCTION text_sx_lt(text, text) RETURNS boolean AS
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'select soundex($1) < soundex($2)'
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LANGUAGE SQL;
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CREATE FUNCTION text_sx_gt(text, text) RETURNS boolean AS
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'select soundex($1) > soundex($2)'
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LANGUAGE SQL;
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CREATE FUNCTION text_sx_le(text, text) RETURNS boolean AS
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'select soundex($1) <= soundex($2)'
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LANGUAGE SQL;
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CREATE FUNCTION text_sx_ge(text, text) RETURNS boolean AS
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'select soundex($1) >= soundex($2)'
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LANGUAGE SQL;
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CREATE FUNCTION text_sx_ne(text, text) RETURNS boolean AS
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'select soundex($1) <> soundex($2)'
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LANGUAGE SQL;
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DROP OPERATOR #= (text, text);
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CREATE OPERATOR #= (leftarg=text, rightarg=text, procedure=text_sx_eq, commutator = #=);
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SELECT * FROM s WHERE text_sx_eq(nm, 'john');
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SELECT * FROM s WHERE s.nm #= 'john';
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SELECT * FROM s WHERE difference(s.nm, 'john') > 2;
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