在SQL变量中存储多个变量，并将其用于删除表中的条目

Question

Hi i was wondering how could a deletetion of multiple values can be achieved in a table.

I have a following query:

DELETE FROM dbo.MainJobs WHERE  @MainJobId =IDKey
declare @subjob nvarchar;
SET @subjob = (SELECT SubJobFamily FROM dbo.Jobz where  JobFamily = @MainJobId ) --has mutiple values in the table
Delete dbo.Jobz where JobFamily = @MainJobId
DELETE dbo.Relationship1 where SubJobs =  @subjob  --deletion of multiple rows

To summarize i am trying to delete the relationship of multiple sub jobs however there are multiple sub jobs that are linked to the main job family and I am getting an error while storing it into the variable - @subjob . ANy help would be appreciated.

Answer 1

You can not store multiple values to a scalar variable, you need to have a table type to store the multiple values.

You can try like following using a temporary table.

DECLARE @subjob NVARCHAR(20); 

SELECT subjobfamily 
INTO   #t 
FROM   dbo.jobz 
WHERE  jobfamily = @MainJobId 

DELETE dbo.jobz 
WHERE  jobfamily = @MainJobId 

DELETE dbo.relationship1 
WHERE  subjobs IN (SELECT subjobfamily 
                   FROM   #t) 
drop table #t

Also you need to specify the length of your @subjob variable, if you don't specify the length, it will just take the first character only.

Change following declaration

declare @subjob nvarchar;

to something like

declare @subjob nvarchar(100)

Answer 2

There are two types of variables in SQL Server - there are scalar variables (all built in data types are scalar variables) and there are table variables. You can declaring a table variable either by using a user-defined table type as it's type, or by specifying it as a table with all it's columns.

Suppose you have a UDT like this:

create type dbo.intList as table
(
    val int 
) 

you can declare a variable of that type, and it will be a table variable containing a single int column called val:

declare @MyIntsTable As dbo.intList

Or you can declare a table variable like this:

declare @MyIntsTable as table
(
    val int 
)

However, I don't think you need to use a table variable in this situation. Seems to me like you need something like this:

BEGIN TRANSACTION

    BEGIN TRY

        DELETE 
        FROM dbo.MainJobs 
        WHERE @MainJobId =IDKey

        DELETE dbo.Relationship1 
        WHERE SubJobs IN
        (
            SELECT SubJobFamily 
            FROM dbo.Jobz 
            WHERE  JobFamily = @MainJobId
        )

        DELETE
        FROM dbo.Jobz 
        WHERE JobFamily = @MainJobId

    END TRY
    BEGIN CATCH
        IF @@TRANCOUNT > 0
            ROLLBACK TRANSACTION
    END CATCH

IF @@TRANCOUNT > 0
    ROLLBACK TRANSACTION

I've wrapped the delete statements in a transaction because I'm assuming you need all of them to succeed, but if one fails you want all to fail.

Answer 3

This would be done in 2 step process.

First create a set of your required ID in comma separated string, then on the basis of each value in string delete your whole record from reference tables.

For creating comma separated string you can use 'stuff' or 'coalesce' .

    DELETE FROM dbo.MainJobs WHERE  @MainJobId =IDKey
    declare @subjob nvarchar;
    SET @subjob = (SELECT SubJobFamily FROM dbo.Jobz where  JobFamily = @MainJobId ) -- use stuff or coalesce to get your result in comma separated string then use t-sql to delete your record
    Delete dbo.Jobz where JobFamily = @MainJobId
    DELETE dbo.Relationship1 where SubJobs =  @subjob  -- use t-sql over there

Or

Another option is use cursor to fetch each record in loop and perform your required action from that record.

    DELETE FROM dbo.MainJobs WHERE  @MainJobId =IDKey
    declare @subjob nvarchar;
    ----- use cursor over there to get each record one by one on SELECT SubJobFamily FROM dbo.Jobz where  JobFamily = @MainJobId
    SET @subjob = (SELECT SubJobFamily FROM dbo.Jobz where  JobFamily = @MainJobId ) --has mutiple values in the table
    Delete dbo.Jobz where JobFamily = @MainJobId
    DELETE dbo.Relationship1 where SubJobs =  @subjob  --deletion of multiple rows