如何编写连接两个表的查询并获取sql中的数据？

Question

我有两个表在我的数据库假设

OLD_TABLE

id name  type 
322 , shubham, 0 

NEW_TABLE

id member_id 
322 , 5 
322 , 7 

，所以我必须让这样的事情

select c.id, cm.member_id, 
     case when existes cm.member_id = 5 as new_table 
from old_table c left join 
    new_table cm 
    on c.id = cm.id 
where c.type = 0 
order by c.id desc 
limit 200 

Answer 1

的加入似乎是正确的，而不是案件
您应该使用的情况下，当......那么......到底例如：

 select 
     c.id, 
     cm.member_id, 
     case when cm.member_id = 5 then cm.member_id end as new_table 
    from old_table c 
    left join new_table cm on c.id = cm.id 
    where c.type = 0 
    order by c.id desc limit 200 

或

select 
     c.id, 
     cm.member_id, 
     case when cm.member_id = 5 then cm.member_id else 0 end as new_table 
    from old_table c 
    left join new_table cm on c.id = cm.id 
    where c.type = 0 
    order by c.id desc limit 200