1.mysql之select

1.1 字符串转对应的名称

一串用户id字符串(逗号分割)，需要转成对应的用户昵称

-- view_members        用户id集合（uid1,uid1,uid3）
-- view_member_names   用户昵称集合（uname1,uname1,uname3）
select   
 tb.*,
(select group_concat(tu.name) from t_user tu where find_in_set(tu.id,t.view_members)) as view_member_names   
from t_bussiness tb

1.2 往前推15天

-- 方式1
select 
      date_sub(CURRENT_DATE, interval (@start_rn:=@start_rn +1)+1 day) startDate,
      date_sub(CURRENT_DATE, interval (@end_rn:=@end_rn+1)  day) endDate
from (select 1 from mysql.help_topic) a,(select @start_rn:=0,@end_rn:=0) b limit 15
-- 方式2
select 
      @start_rn,
      date_sub(str_to_date('2022-05-10','%Y-%m-%d') , interval (@start_rn:=@start_rn +1)-1 day) startDate
from (select 1 from mysql.help_topic) a,(select @start_rn:=0) b 
where @start_rn<=datediff(str_to_date('2022-05-10','%Y-%m-%d'),str_to_date('2022-05-01','%Y-%m-%d'))

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