在 Else 子句中重用子查询的值

Question

is there any way i can use the value of X in the if clause in the else clause

if @bid_value>(SELECT  MAX(bid_value) AS X FROM dbo.auctionDetails WHERE status = 0 AND vehicle_id=@vid GROUP BY vehicle_id)
            BEGIN
                //some code      
            END 
ELSE IF X=NULL
        BEGIN
        //some code
        END

Answer 1

You would typically assign the results of the query to a variable.

If you are running SQL Server:

DECLARE @max_bid_value INT;

SELECT @max_bid_value = MAX(bid_value)
FROM dbo.auctionDetails 
WHERE status = 0 AND vehicle_id = @vid;

IF @bid_value > @max_bid_value
BEGIN
    //some code      
END 
...

Note that I removed the GROUP BY clause from the original query - I think that this makes it clearer that it should always return a scalar value.

Note that if you want to check if a variable is null , you need @bid is null rather than @bid = null .

Answer 2

Why don't you create a var for the value?

DECLARE @maxValue INT

SELECT @maxValue = MAX(bid_value) 
FROM dbo.auctionDetails 
WHERE status = 0 AND vehicle_id = @vid 

IF (@bid_value > @maxValue)
BEGIN
    // some code
END
ELSE IF (@maxValue IS NULL)
BEGIN
    // some code
END 

A comment about how you are getting the MAX value: As you are filtering by vehicle_id = @vid, you don't need GROUP BY clause since you will get results for only one value of vahicle_id

Answer 3

Your query should be like below:

    DECLARE @X INT
        SET @X = (SELECT  MAX(bid_value) AS X FROM dbo.auctionDetails WHERE status = 0 AND vehicle_id=@vid);
   IF @bid_value>@MAX   
     BEGIN
            //some code      
      END 
        ELSE IF X=NULL
      BEGIN
            //some code
       END