Question

I need to have a generated query:

SELECT @numberOfRecords = COUNT(*) FROM Car WHERE CarId not in (Select CarId from CarData)

At the moment I have :

DECLARE @sql NVARCHAR(255)
SET @sql='Select CarId from CarData'

DECLARE @numberOfRecords BIGINT
SELECT @numberOfRecords = COUNT(*) FROM Car WHERE CarId not in (@sql)

I was trying other various combinations, like '(' nut it doesn’t work.
What I need to change to have it working?

Answer 1

What you are looking for is called dynamic sql, there is numerous articles about it, you’ll need to use sp_executesql if you are using SQL Server

there is an example here for something similar to what you are trying to do

your solution should look something like this

DECLARE @carIdSql        NVARCHAR(255),
        @sql             NVARCHAR(MAX),
        @ParamDefinition NVARCHAR(MAX),
        @numberOfRecords BIGINT

SET @carIdSql='Select CarId from CarData';

SET @sql =
N'SELECT @numberOfRecordsOUT = COUNT(*) 
  FROM Car WHERE CarId not in (' + @carIdSql + ')'

SET @ParamDefinition = '@numberOfRecordsOUT BIGINT OUTPUT';

EXECUTE sp_executesql
  @sql,
  @ParamDefinition,
  @numberOfRecordsOUT = @numberOfRecords OUTPUT;

SELECT @numberOfRecords