Is it possible to delete from multiple tables in the same SQL statement?

Question

It\'s possible to delete using join statements to qualify the set to be deleted, such as the following:

DELETE J
FROM Users U
inner join LinkingTable J on U.         


        

Answer 1

The only way I could think of is logically break the bi-directional foreign keys in a procedural way.

This approach can have huge impact to your application side if you don't have some flags for visualization state or status

Something like

1. INSERT dummy not visible rows to Users (with something like Id = -1 for dummy values)

2. Add to LinkingTable an alternative column to point back to Users, I'll call it U_ComesFrom

   ALTER TABLE LinkingTagble ADD U_ComesFrom_U_id INT DEFAULT(-1)

3. Add FOREIGN KEY with a NOCHECK

   ALTER TABLE LinkingTable WITH NOCHECK
   FOREIGN KEY (U_ComesFrom_U_id)
   REFERENCES Users (Id) ;

4. Add to Users column

   ALTER TABLE Users ADD MarkedForDeletion BIT NOT NULL DEFAULT(0)

Then your SQL would look like

BEGIN TRANSACTION
    UPDATE J
    SET U_Comes_From_U_id = U_ID, U_id = -1 -- or some N/R value that you define in Users
    FROM Users U
    inner join LinkingTable J on U.id = J.U_id
    inner join Groups G on J.G_id = G.id
    WHERE G.Name = 'Whatever'
    and U.Name not in ('Exclude list')

    UPDATE U
    SET MarkedForDeletion = 1
    FROM Users
    inner join LinkingTable J on U.id = J.U_ComesFrom_U_id 
    WHERE U_id > 0

    DELETE FROM LinkingTable 
    WHERE U_ComesFrom_U_id > 0

    DELETE FROM Users
    WHERE MarkedForDeletion = 1

COMMIT

This approach would impact the performance since each transaction would be at least 4 DML operations per bi-directional keys.