MySQL if 语句与 where 子句一起使用

Question

如何向查询添加附加 WHERE 子句。有这样的查询:

SELECT round(Sum(Zarada), 2) AS Zarada, 
       cms_cart_customers.Firstname,
       cms_cart_wallet.WalletType as WW ,
       cms_cart_customers.Lastname, 
       FROM_UNIXTIME(`cms_cart_customers`.`d_ins`, " %d.%m.%Y") AS Datum_formatiran 
  FROM (cms_cart_customers) 
  LEFT JOIN cms_cart_wallet
    ON cms_cart_wallet.IdBuyer =cms_cart_customers.Id 
  WHERE `cms_cart_customers`.`IDReferral` = '199' AND
        if(ww = 7) THEN ' cms_cart_wallet.WalletType =7' END IF 
  GROUP BY cms_cart_customers.Id

如果选择 cms_cart_wallet.WalletType 作为 Ww 然后添加新的额外子句 WHERE cms_cart_wallet.WalletType is 7 。这样可以吗？？？

Answer 1

您可以通过在左连接中添加一个子句来实现这一点，如下所示。

SELECT round(Sum(Zarada), 2) AS Zarada, cms_cart_customers.Firstname,cms_cart_wallet.WalletType as WW ,cms_cart_customers.Lastname, FROM_UNIXTIME(cms_cart_customers.d_ins, " %d.%m.%Y") AS Datum_formatiran FROM (cms_cart_customers) LEFT JOIN cms_cart_wallet ON cms_cart_wallet.IdBuyer =cms_cart_customers.Id and cms_cart_wallet.WalletType =7 WHERE cms_cart_customers.IDReferral = '199'  GROUP BY cms_cart_customers.Id