在MySQL中嵌套IF ELSE

Question

我想執行下面的存儲過程，但它給了我一個錯誤。更新訂單表後，在標誌1內我想檢查另一個條件，如果這是真的，那麼我想運行另一個更新查詢。我在SQL Server中用臨時表試過了，它工作正常。請幫幫我。

誤差如下：

腳本行：4您的SQL語法錯誤;檢查對應於你的MySQL服務器版本正確的語法使用 接近手動 「從產品PR INNER JOIN（SELECT PR.ID AS產品ID，（PR.Quantity - OD.Qu」在第35行

DELIMITER $$ 

DROP PROCEDURE IF EXISTS `onlineshop`.`USP_Public_SaveOrder` $$ 
CREATE DEFINER=`root`@`localhost` PROCEDURE `USP_Public_SaveOrder`(IN pint_Flag INT,INOUT pint_ID BIGINT,IN pint_Status INT,IN pint_CustomerID BIGINT,IN pint_ShippingAddressID BIGINT,IN pint_BillingAddresID BIGINT, IN pdec_ShippingCharge DECIMAL(18,2),IN pdec_Tax DECIMAL(18,2),IN pdec_Total DECIMAL(18,2),IN pdte_TransactionDate DATETIME) 
BEGIN 
IF(pint_Flag=0) THEN 
    INSERT INTO orderheader(Status, 
              CustomerID, 
              ShippingAddressID, 
              BillingAddressID, 
              ShippingCharge, 
              Tax, 
              Total, 
              TransactionDate) 
          VALUES (pint_Status, 
              pint_CustomerID, 
              pint_ShippingAddressID, 
              pint_BillingAddresID, 
              pdec_ShippingCharge, 
              pdec_Tax, 
              pdec_Total, 
              pdte_TransactionDate); 
     SET pint_ID=LAST_INSERT_ID(); 

ELSEIF(pint_Flag=1) THEN 
    UPDATE orderheader 
    SET  Status = pint_Status, 
       CustomerID = pint_CustomerID, 
       ShippingAddressID = pint_ShippingAddressID, 
       BillingAddressID = pint_BillingAddresID, 
       ShippingCharge = pdec_ShippingCharge, 
       Tax = pdec_Tax, 
       Total = pdec_Total, 
       TransactionDate = pdte_TransactionDate 
    WHERE ID=pint_ID; 
    IF(pint_Status=2) THEN 
    UPDATE product SET Quantity = A.remain 
    FROM product PR 
    INNER JOIN (SELECT PR.ID AS ProductID, (PR.Quantity - OD.Quantity) AS remain 
       FROM product P 
       INNER JOIN orderdetail OD ON OD.ProductID = P.ID AND OD.OrderID = pint_ID) A ON PR.ID = A.ProductID 
    ELSE 
    RETURN 
    END IF; 
END IF; 
END $$ 

DELIMITER ; 

Answer 1

修改您UPDATE塊如下，並嘗試

IF(pint_Status=2) THEN 
    UPDATE product PR 
    INNER JOIN (SELECT PR.ID AS ProductID, (PR.Quantity - OD.Quantity) AS remain 
       FROM product P 
       INNER JOIN orderdetail OD ON OD.ProductID = P.ID AND OD.OrderID = pint_ID 
       ) A ON PR.ID = A.ProductID 
    SET PR.Quantity = A.remain; 
ELSE 
    RETURN 
END IF; 

Answer 2

檢查UPDATE語句的語法：。14.2.11 UPDATE Syntax

. 
. 
. 
UPDATE product SET Quantity = A.remain 
FROM product PR 
    INNER JOIN (SELECT PR.ID AS ProductID, (PR.Quantity - OD.Quantity) AS remain 
       FROM product P 
       INNER JOIN orderdetail OD ON 
        OD.ProductID = P.ID AND 
        OD.OrderID = pint_ID 
      ) A ON PR.ID = A.ProductID -- ; <- Add semicolon 
. 
. 
. 
/*ELSE 
    RETURN*/ 

存儲過程不需要RETURN。

Answer 3

MySQL的UPDATE語法不使用FROM關鍵字。如果您想要爲正在更新的表指定別名，只需將其放在UPDATE tablename子句之後即可。而在你的子查詢中，你應該使用別名P，而不是PR。

UPDATE PRODUCT AS PR 
INNER JOIN (SELECT P.ID AS ProductID, (P.Quantity - OD.Quantity) AS remain 
      FROM product P 
      INNER JOIN orderdetail OD ON OD.ProductID = P.ID AND OD.OrderID = pint_ID) A ON PR.ID = A.ProductID 
SET PR.Quantity = A.remain 

實際上，有沒有必要使用子查詢，剛剛加入PRODUCT與orderdetail直接。

UPDATE PRODUCT AS PR 
INNER JOIN orderdetail AS OD ON OD.ProductID = PR.ID 
SET PR.Quantity = PR.Quantity - OD.Quantity 
WHERE OD.OrderID = pintID