MySQL常用字符串函数

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@see MySQL 5.1 Reference Manual
12.3 String Functions

SELECT SUBSTRING("The world's most popular open source database.", 5);
#->world's most popular open source database.

SELECT SUBSTRING("The world's most popular open source database.", 5, 5);
#->world

SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
#->'barxxx'

SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
#->'bar'

SELECT TRIM(TRAILING 'xyz' FROM 'xxyzbarxxyz');
#->'xxyzbarx'

SELECT RIGHT('foobarbar', 4);
#->'rbar'

SELECT LEFT('foobarbar', 4);
#->'foob'

SELECT REVERSE('barcelona');
#->'anolecrab'

SELECT REPLACE('www.mysql.com', 'w', 'Ww');
#->'WwWwWw.mysql.com'

SELECT LOWER('BARCELONA');
#->'barcelona'

SELECT UPPER('barcelona');
#->'BARCELONA'

SELECT INSERT('Quadratic', 3, 4, 'What');
#->'QuWhattic'

SELECT CHAR_LENGTH('中国CHINA');
#->7

SELECT LENGTH('中国CHINA');

#->11

SELECT CONCAT('My', 'S', 'QL');#->'MySQL'