In SQL Server 2005, can I do a cascade delete without setting the property on my tables?

Question

I have a database full of customer data. It\'s so big that it\'s really cumbersome to operate on, and I\'d rather just slim it down to 10% of the customers, which is plenty

Answer 1

Post here a script that will work with foreign keys contain more than one column.

create procedure usp_delete_cascade (
@TableName varchar(200), @Where nvarchar(1000)
) as begin

declare @to_delete table (
    id int identity(1, 1) primary key not null,
    criteria nvarchar(1000) not null,
    table_name varchar(200) not null,
    processed bit not null default(0),
    delete_sql varchar(1000)
)
            DECLARE @MyCursor CURSOR

declare         @referencing_column_name varchar(1000)
declare         @referencing_table_name varchar(1000)
 declare @Sql nvarchar(4000)
insert into @to_delete (criteria, table_name) values ('', @TableName)


declare @id int, @criteria nvarchar(1000), @table_name varchar(200)
while exists(select 1 from @to_delete where processed = 0) begin
    select top 1 @id = id, @criteria = criteria, @table_name = table_name from @to_delete where processed = 0 order by id desc
        SET @MyCursor = CURSOR FAST_FORWARD
        FOR
        select referencing_column.name as column_name,
            referencing_table.name as table_name
        from  sys.foreign_key_columns fk
            inner join sys.columns referencing_column on fk.parent_object_id = referencing_column.object_id 
                and fk.parent_column_id = referencing_column.column_id 
            inner join  sys.columns referenced_column on fk.referenced_object_id = referenced_column.object_id 
                and fk.referenced_column_id = referenced_column.column_id 
            inner join  sys.objects referencing_table on fk.parent_object_id = referencing_table.object_id 
            inner join  sys.objects referenced_table on fk.referenced_object_id = referenced_table.object_id 
            inner join  sys.objects constraint_object on fk.constraint_object_id = constraint_object.object_id
        where referenced_table.name = @table_name
            and referencing_table.name != referenced_table.name

        OPEN @MyCursor
        FETCH NEXT FROM @MYCursor
        INTO @referencing_column_name, @referencing_table_name

        WHILE @@FETCH_STATUS = 0

        BEGIN
            PRINT @referencing_column_name
            PRINT @referencing_table_name
                    update @to_delete set criteria = criteria + ' AND '+@table_name+'.'+@referencing_column_name+'='+ @referencing_table_name+'.'+@referencing_column_name
                    where table_name = @referencing_table_name

                    if(@@ROWCOUNT = 0)
                    BEGIN
                            --if(@id <> 1)
                            --BEGIN
                                insert into @to_delete (criteria, table_name)
                                VALUES( ' LEFT JOIN '+@table_name+' ON '+@table_name+'.'+@referencing_column_name+'='+ @referencing_table_name+'.'+@referencing_column_name+ @criteria,
                                @referencing_table_name
                                )
                            --END
                            --ELSE
                            --BEGIN
                                --insert into @to_delete (criteria, table_name)
                                --VALUES( ' LEFT JOIN '+@table_name+' ON '+@table_name+'.'+@referencing_column_name+'='+ @referencing_table_name+'.'+@referencing_column_name,
                                --@referencing_table_name
                                --)
                            --END
                    END
                        FETCH NEXT FROM @MYCursor
            INTO @referencing_column_name, @referencing_table_name
        END


        CLOSE @MyCursor 
        DEALLOCATE @MyCursor 
    update @to_delete set
        processed = 1
    where id = @id
end

--select 'print ''deleting from ' + table_name + '...''; delete from [' + table_name + '] where ' + criteria from @to_delete order by id desc

--select id, table_name, criteria, @Where from @to_delete order by id desc

select @id = max(id) from @to_delete
while (@id >= 1)
begin
    select @criteria = criteria, @table_name = table_name from @to_delete where id = @id
    set @Sql = 'delete [' + @table_name + '] from [' + @table_name + '] ' + @criteria+' WHERE '+@Where
    exec (@Sql)
    PRINT @Sql

    -- Next record
    set @id = @id - 1
end
end

Answer 2

Combining your advice and a script I found online, I made a procedure that will produce SQL you can run to perform a cascaded delete regardless of ON DELETE CASCADE. It was probably a big waste of time, but I had a good time writing it. An advantage of doing it this way is, you can put a GO statement between each line, and it doesn't have to be one big transaction. The original was a recursive procedure; this one unrolls the recursion into a stack table.

create procedure usp_delete_cascade (
    @base_table_name varchar(200), @base_criteria nvarchar(1000)
)
as begin
    -- Adapted from http://www.sqlteam.com/article/performing-a-cascade-delete-in-sql-server-7
    -- Expects the name of a table, and a conditional for selecting rows
    -- within that table that you want deleted.
    -- Produces SQL that, when run, deletes all table rows referencing the ones
    -- you initially selected, cascading into any number of tables,
    -- without the need for "ON DELETE CASCADE".
    -- Does not appear to work with self-referencing tables, but it will
    -- delete everything beneath them.
    -- To make it easy on the server, put a "GO" statement between each line.

    declare @to_delete table (
        id int identity(1, 1) primary key not null,
        criteria nvarchar(1000) not null,
        table_name varchar(200) not null,
        processed bit not null,
        delete_sql varchar(1000)
    )

    insert into @to_delete (criteria, table_name, processed) values (@base_criteria, @base_table_name, 0)

    declare @id int, @criteria nvarchar(1000), @table_name varchar(200)
    while exists(select 1 from @to_delete where processed = 0) begin
        select top 1 @id = id, @criteria = criteria, @table_name = table_name from @to_delete where processed = 0 order by id desc

        insert into @to_delete (criteria, table_name, processed)
            select referencing_column.name + ' in (select [' + referenced_column.name + '] from [' + @table_name +'] where ' + @criteria + ')',
                referencing_table.name,
                0
            from  sys.foreign_key_columns fk
                inner join sys.columns referencing_column on fk.parent_object_id = referencing_column.object_id 
                    and fk.parent_column_id = referencing_column.column_id 
                inner join  sys.columns referenced_column on fk.referenced_object_id = referenced_column.object_id 
                    and fk.referenced_column_id = referenced_column.column_id 
                inner join  sys.objects referencing_table on fk.parent_object_id = referencing_table.object_id 
                inner join  sys.objects referenced_table on fk.referenced_object_id = referenced_table.object_id 
                inner join  sys.objects constraint_object on fk.constraint_object_id = constraint_object.object_id
            where referenced_table.name = @table_name
                and referencing_table.name != referenced_table.name

        update @to_delete set
            processed = 1
        where id = @id
    end

    select 'print ''deleting from ' + table_name + '...''; delete from [' + table_name + '] where ' + criteria from @to_delete order by id desc
end

exec usp_delete_cascade 'root_table_name', 'id = 123'

Answer 3

I usually just hand write the queries to delete the records I don't want and save that as a .sql file for future reference. The pseudocode is:

1. select id's of records from the main table that I want to delete into a temp table
2. write a delete query for each related table which joins to the temp table.
3. write a delete query for the main table joining to my temp table.

Answer 4

My suggestion is to go ahead and write a script that will add the on delete cascade to each relationship in the database while exporting a list of modified relationships. Then you can reverse the process and remove the on delete cascade command on each table in the list.

Answer 5

Expansion of croisharp's answer to take triggers into consideration, i.e. schema-aware solution that disables all affecting triggers, deletes rows, and enables the triggers.

CREATE PROCEDURE usp_delete_cascade (
@base_table_schema varchar(100),
@base_table_name varchar(200),
@base_criteria nvarchar(1000)
)
as begin

    -- Expects the name of a table, and a conditional for selecting rows
    -- within that table that you want deleted.
    -- Produces SQL that, when run, deletes all table rows referencing the ones
    -- you initially selected, cascading into any number of tables,
    -- without the need for "ON DELETE CASCADE".
    -- Does not appear to work with self-referencing tables, but it will
    -- delete everything beneath them.
    -- To make it easy on the server, put a "GO" statement between each line.

    declare @to_delete table (
            id int identity(1, 1) primary key not null,
            criteria nvarchar(1000) not null,
            table_schema varchar(100),
            table_name varchar(200) not null,
            processed bit not null,
            delete_sql varchar(1000)
    )

    insert into @to_delete (criteria, table_schema, table_name, processed) values (@base_criteria, @base_table_schema, @base_table_name, 0)

    declare @id int, @criteria nvarchar(1000), @table_name varchar(200), @table_schema varchar(100)
    while exists(select 1 from @to_delete where processed = 0) begin
            select top 1 @id = id, @criteria = criteria, @table_name = table_name, @table_schema = table_schema from @to_delete where processed = 0 order by id desc

            insert into @to_delete (criteria, table_schema, table_name, processed)
                    select referencing_column.name + ' in (select [' + referenced_column.name + '] from [' + @table_schema + '].[' + @table_name +'] where ' + @criteria + ')',
                            schematable.name,
                            referencing_table.name,
                            0
                    from  sys.foreign_key_columns fk
                            inner join sys.columns referencing_column on fk.parent_object_id = referencing_column.object_id 
                                    and fk.parent_column_id = referencing_column.column_id 
                            inner join  sys.columns referenced_column on fk.referenced_object_id = referenced_column.object_id 
                                    and fk.referenced_column_id = referenced_column.column_id 
                            inner join  sys.objects referencing_table on fk.parent_object_id = referencing_table.object_id 
                            inner join sys.schemas schematable on referencing_table.schema_id = schematable.schema_id
                            inner join  sys.objects referenced_table on fk.referenced_object_id = referenced_table.object_id 
                            inner join  sys.objects constraint_object on fk.constraint_object_id = constraint_object.object_id
                    where referenced_table.name = @table_name
                            and referencing_table.name != referenced_table.name

            update @to_delete set
                    processed = 1
            where id = @id
    end

    select 'print ''deleting from ' + table_name + '...''; delete from [' + table_schema + '].[' + table_name + '] where ' + criteria from @to_delete order by id desc

    DECLARE @commandText VARCHAR(8000), @triggerOn VARCHAR(8000), @triggerOff VARCHAR(8000)
    DECLARE curDeletes CURSOR FOR
        select
            'DELETE FROM [' + table_schema + '].[' + table_name + '] WHERE ' + criteria,
            'ALTER TABLE [' + table_schema + '].[' + table_name + '] DISABLE TRIGGER ALL',
            'ALTER TABLE [' + table_schema + '].[' + table_name + '] ENABLE TRIGGER ALL'
        from @to_delete order by id desc

    OPEN curDeletes
    FETCH NEXT FROM curDeletes INTO @commandText, @triggerOff, @triggerOn

    WHILE(@@FETCH_STATUS=0)
    BEGIN
        EXEC (@triggerOff)
        EXEC (@commandText)
        EXEC (@triggerOn)
        FETCH NEXT FROM curDeletes INTO @commandText, @triggerOff, @triggerOn
    END
    CLOSE curDeletes
    DEALLOCATE curDeletes
end

Answer 6

Kevin post is incomplete, his t-sql sp only prints the command, to execute these command, before last end add this

DECLARE @commandText VARCHAR(8000)
        DECLARE curDeletes CURSOR FOR
            select 'delete from [' + table_name + '] where ' + criteria from @to_delete order by id desc

        OPEN curDeletes
        FETCH NEXT FROM curDeletes
        INTO
            @commandText

        WHILE(@@FETCH_STATUS=0)
        BEGIN
            EXEC (@commandText)
            FETCH NEXT FROM curDeletes INTO @commandText
        END
        CLOSE curDeletes
        DEALLOCATE curDeletes