trim只能是空格
trim的语法 TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str)
BOTH 首尾
LEADING 首
TRAILING 尾
remstr 要去掉的字符
str 要处理的字符串
例
SELECT TRIM(BOTH ',' FROM ',,aaaa,,,'); aaaa 复制
SELECT TRIM(BOTH ',' FROM ',,aaaa,,,'); aaaa