Delete data from dependent tables

Question

Is there a query in SQL Server 2008 which will delete data from all dependent tables as well, along with the selected table?

My apologies for not having elaborated on the question. I know that Cascade Delete would work fine, but my application connects to a 3rd party SQL Server db. I have a few Unit Tests which insert into the target table and the dependent tables. Unfortunately the constraints on the target table are not On Delete Cascade and I cannot create them or have them created. I am looking for a generic way of traversing through the dependencies and deleting data in the right order.

Answer 1

As there are foreign key relationships, following script could get you started mimicking a cascaded delete.

DECLARE @TableName VARCHAR(32)
DECLARE @PrimaryKey VARCHAR(32)

SET @TableName = 'MasterTable'
SET @PrimaryKey = '1'

SELECT  'DELETE FROM '
        + fks.name + '.' + fkt.name
        + ' WHERE '
        + pc.name 
        + ' = '
        + @PrimaryKey
        , fko.name as [FK Name]
        , fk.constraint_column_id as [Col Order]
        , fks.name + '.' + fkt.name as [FK table]
        , pc.name as [FK column]
        , rcs.name + '.' + rct.name as [PK table]
        , rc.name as [PK column]
FROM    sys.foreign_key_columns fk
        -- FK columns
        INNER JOIN sys.columns pc ON fk.parent_object_id = pc.object_id
                                     AND fk.parent_column_id = pc.column_id
        INNER JOIN sys.objects fkt ON pc.object_id = fkt.object_id
        INNER JOIN sys.schemas as fks ON fks.schema_id = fkt.schema_id
        -- referenced PK columns
        INNER JOIN sys.columns rc ON fk.referenced_object_id = rc.object_id
                                     AND fk.referenced_column_id = rc.column_id
        INNER JOIN sys.objects rct ON rc.object_id = rct.object_id
        INNER JOIN sys.schemas as rcs ON rcs.schema_id = rct.schema_id
        -- foreign key constraint name
        INNER JOIN sys.objects fko ON fk.constraint_object_id = fko.object_id
WHERE   rct.Name = @TableName

Answer 2

To do that you set up a constraint between the tables with cascading delete. You can do that in a diagram by dragging a connection between fields and editing the properties, or using a query:

 alter table SomeTable
 add constraint SomeConstraint
 foreign key (SomeField) references SomeOtherTable (SomeOtherField) 
 on delete cascade