Question

I have a table ParentTable in which I have parentId as primary key.

Now I have three child tables ChildTable1, ChildTable2 and ChildTable3.

• in ChildTable1, primary key is ch1Id and foreign key is fkparentId (pk from ParentTable)

• in ChildTable2, primary key is ch2Id and foreign keys are fkparentId and fkch1Id (primary key from ChildTable1)

• in ChildTable3, primary key is ch3Id and foreign keys are fkparentId, fkch1Id and fkch2Id (primary key from ChildTable2).

And this goes on..

I want to write a query to delete these tables hierarchially in the following manner.

First delete ChildTable3 > then delete ChildTable2 > then delete ChildTable1 and finally delete ParentTable.

I have a vague idea of doing this like

delete from ChildTable3
where fkch2Id = ch2.ch2Id
and fkch1Id = ch1.ch1Id
and fkparentId = p.parentId

then proceeding to ChildTable2 for deletion and so on. Hope I made it clear.

Answer 1

You can do same thing without any query by setting cascade on delete on foreign key definitin.

if you don’t set foreign key definiton on db you can delete records on fkparentId like this.

declare @parentId int = 3

delete from ChildTable3 where fkparentId = @parentId;
delete from ChildTable2 where fkparentId = @parentId;
delete from ChildTable1 where fkparentId = @parentId;
delete from ParentTable where parentId = @parentId;