Question

我有一张表INVENTORY

Create table INVENTORY(){
      INVENID int indentity,      -- inventory ID
      PRODUCTID varchar(10), --product id
      QUANTUM int,      -- quantum
      QUANTUMINPUT int, -- quantum input
      QUANTUMOUTPUT int, -- quantum output
}

我创建了触发器：

Create trigger trig_cal
on INVENTORY
after insert,update
as
if(UPDATE(QUANTUMINPUT))
begin
UPDATE INVENTORY set QUANTUM  = QUANTUM + QUANTUMINPUT
end
else if(UPDATE(QUANTUMOUTPUT))
begin
UPDATE INVENTORY set QUANTUM  = QUANTUM - QUANTUMOUTPUT
end

我尝试插入Insert into INVENTORY(PRODUCTID,QUANTUM) values('P01',100) 然后UPDATE INVENTORY set QUANTUMOUTPUT = 1 where PRODUCTID = 'P01' 它返回QUANTUM = 90。这是不对的但是，当我更新QUANTUMOUTPUT或QUANTUMINPUT时，计算错误

Answer 1

尝试使用此触发器代码

   CREATE TABLE INVENTORY
  (
     INVENID       INT,-- inventory ID
     PRODUCTID     VARCHAR(10),--product id
     QUANTUM       INT,-- quantum
     QUANTUMINPUT  INT,-- quantum input
     QUANTUMOUTPUT INT, -- quantum output
  )

ALTER TRIGGER trig_cal
ON INVENTORY
after UPDATE
AS
    IF( UPDATE(QUANTUMINPUT) )
      BEGIN
          UPDATE INV
          SET    INV.QUANTUM = INS.QUANTUM + INS.QUANTUMINPUT
          FROM   INVENTORY INV
                 JOIN INSERTED INS
                   ON ISNULL(INS.INVENID, 0) = ISNULL(INV.INVENID, 0)
                      AND ISNULL(INS.PRODUCTID, 0) = ISNULL(INV.PRODUCTID, 0)
      END
    ELSE IF( UPDATE(QUANTUMOUTPUT) )
      BEGIN
          UPDATE INV
          SET    INV.QUANTUM = INS.QUANTUM - INS.QUANTUMOUTPUT
          FROM   INVENTORY INV
                 JOIN INSERTED INS
                   ON ISNULL(INS.INVENID, 0) = ISNULL(INV.INVENID, 0)
                      AND ISNULL(INS.PRODUCTID, 0) = ISNULL(INV.PRODUCTID, 0)
      END

    INSERT INTO INVENTORY
                (PRODUCTID,
                 QUANTUM)
    VALUES     ('P01',
                100)

    UPDATE INVENTORY
    SET    QUANTUMOUTPUT = 1
    WHERE  PRODUCTID = 'P01'

    UPDATE INVENTORY
    SET    QUANTUMINPUT = 1
    WHERE  PRODUCTID = 'P01'

SQL触发器在列表之间计算

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