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mysq函数concat_ws

CONCAT_WS() concat with separator

CONCAT_WS('|',a)连接成一行

CONCAT_WS('|',  2,8  ) ==2|8
CONCAT(',',11,22)=,1122

区别

CONCAT(',',11,22,null)=null,中有一个参数为NULL，则查询结果为NULL

CONCAT_WS(',',11,22,null)=11,22；有NULL则去掉，其余的不变

SELECT CONCAT('_','11','22',null)=null

SELECT CONCAT_ws('_','11','22',null,'33')=11_22_33

例如，表aaaa

id    	name
1		a11
1		a111
1		a1111
2		a22
2		a222
3		a33

SELECT id,
	concat_ws(',',GROUP_CONCAT(name)) as name_1
from aaaa
group by id

查询结果

1a11,a111,a1111

2a22,a222

3a33

2021-11-13