MySQL UPDATE字段，其中在同一个表中的另一个字段计数= 1

Question

请有人给我下面的正确语法。

MySQL UPDATE tblcontact SET MainContact = 1 
WHERE COUNT(tblcontact.CompanyID) = 1 
GROUP BY tblcontact.CompanyID 

Answer 1

我明白了。如果只有一条记录，您希望将该字段设置为1。试试这个：

UPDATE tblcontact c join 
     (select CompanyID, count(CompanyID) as cnt 
     from tblcontact 
     group by CompanyId 
     ) cc 
     on c.CompanyId = cc.CompanyId and cnt = 1 
    SET c.MainContact = 1 ;