常用的MySQL字符串函数详细攻略

SELECT CHARACTER_LENGTH("abcd") AS ‘返回字符串长度';

SELECT CONCAT("ABC",'DEF','王五') AS ‘合并后的字符串';

SELECT CONCAT_WS('-','abc','def','qwe') AS ；‘合并字符串';

SELECT FIELD('a','b','c','a','d')‘位置';

SELECT FIND_IN_SET('a','b,d,e,f,g,a') '位置‘;

SELECT FORMAT(1234456.789,2)'格式化数字‘;

SELECT INSERT("bilibili.com",3,1,"github") '替换后的内容‘;-- bigithubibili.com

SELECT LOCATE('bc','a2defgbc') '位置‘;

SELECT LCASE('DDsaADADAssdIi') '转化小写字母‘;

SELECT LOWER('SHSHhshshsSHSHS') '转化小写字母‘;

SELECT UCASE("DDsaADADAssdIi")‘转化为大写字母';

SELECT UPPER("ddDDsaADADAssdIi")‘转化为大写字母';

SELECT LPAD('abc',10,'jk') ‘填充后的字符串';-- jkjkjkjabc

SELECT RPAD('abc',10,'jk') ‘填充后的字符串';-- abcjkjkjkj

SELECT LENGTH('   adc   bjk   ');-- 15字符
SELECT LTRIM('   adc   bjk   ') '去除字符串S开始处的空格';

SELECT LENGTH(RTRIM('   adc   bjk   ')) ‘去除字符串结尾空格并输出字符串数量12';

SELECT LENGTH(TRIM('   adc   bjk   ')) ‘去除字符串首尾空格并输出字符串长度为9;

SELECT MID('abcdefjklmn',3,5) '从第三个字符开始截取五个字符;-- cdefj

SELECT SUBSTRING('abcdefghijklmn',3,5) ‘相当于MID';

SELECT SUBSTR('abcdefghijklmn',3,5) ‘和上面差不多';-- cdefj

SELECT SUBSTRING_INDEX('a*b','*',1);-- a

SELECT SUBSTRING_INDEX('a*b','*',-1);-- b

SELECT POSITION('a' IN 'fhsabede') '位置';

SELECT REPEAT('I LOVE YOU',10) '重复后的字符串';

SELECT REPLACE('abcabcqwabc','a','A') '替换后的字符串';

SELECT REVERSE('abcd') '反转后的字符串';

SELECT LEFT('abcdefg',3) '前3个字符';

SELECT RIGHT('abcdefg',3) '后3个字符';

SELECT LENGTH(SPACE(10)) '空格字符个数';

SELECT STRCMP('abc','abc'); -- 0

SELECT STRCMP('abc','ABC'); -- 0
SELECT STRCMP('abcd','abc');-- 1

SELECT STRCMP('abc','abcd'); -- -1