Remove ON DELETE CASCADE on foreign keys for several tables - sql-server

Question

I have several tables with a foreign key constraint that has the option ON DELETE CASCADE. Every table belongs to the same schema called datasets.
I'm able to retrieve the complete list of tables using :
SELECT *
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA ='datasets'
For each table I would like to remove the ON DELETE CASCADE option on the foreign key constraint named FK_[TABLENAME]_SerieID where [TABLENAME] corresponds to the name of the table (and SerieId is the same foreign key across tables).
I am able to perform the operation for a particular table, for instance the table called Table1 using :
ALTER TABLE datasets.Table1
DROP CONSTRAINT FK_Table1_SerieID
ALTER TABLE datasets.Table1
ADD CONSTRAINT FK_Table1_SerieID
FOREIGN KEY (Serie_Id) REFERENCES[dbo].[Serie](SerieID)
ON DELETE NO ACTION
GO
I would like to perform the above operation for each table that belong to the schema datasets . I'm new to T-SQL and I don't know how to do it.
Should I use a cursor? Can you help me with this?
I'm using SQL Server 2016.

Answer 1

I would not reinvent the wheel. There is excellent script written by Aaron Bertrand: Drop and Re-Create All Foreign Key Constraints in SQL Server.
You could easily extend it to handle NO ACTION case and specific schema by adding simple WHERE restriction:
DECLARE #drop NVARCHAR(MAX) = N'',
#create NVARCHAR(MAX) = N'';
-- drop is easy,just build a simple concatenated list from sys.foreign_keys:
SELECT #drop += N'
ALTER TABLE ' + QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name)
+ ' DROP CONSTRAINT ' + QUOTENAME(fk.name) + ';'
FROM sys.foreign_keys AS fk
INNER JOIN sys.tables AS ct
ON fk.parent_object_id = ct.[object_id]
INNER JOIN sys.schemas AS cs
ON ct.[schema_id] = cs.[schema_id]
WHERE delete_referential_action_desc <> 'NO_ACTION' -- here
AND cs.name = 'datasets';
-- create is a little more complex. We need to generate the list of
-- columns on both sides of the constraint, even though in most cases
-- there is only one column.
SELECT #create += N'
ALTER TABLE '
+ QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name)
+ ' ADD CONSTRAINT ' + QUOTENAME(fk.name)
+ ' FOREIGN KEY (' + STUFF((SELECT ',' + QUOTENAME(c.name)
-- get all the columns in the constraint table
FROM sys.columns AS c
INNER JOIN sys.foreign_key_columns AS fkc
ON fkc.parent_column_id = c.column_id
AND fkc.parent_object_id = c.[object_id]
WHERE fkc.constraint_object_id = fk.[object_id]
ORDER BY fkc.constraint_column_id
FOR XML PATH(N''), TYPE).value(N'.[1]', N'nvarchar(max)'),1,1,N'')
+ ') REFERENCES ' + QUOTENAME(rs.name) + '.' + QUOTENAME(rt.name)
+ '(' + STUFF((SELECT ',' + QUOTENAME(c.name)
-- get all the referenced columns
FROM sys.columns AS c
INNER JOIN sys.foreign_key_columns AS fkc
ON fkc.referenced_column_id = c.column_id
AND fkc.referenced_object_id = c.[object_id]
WHERE fkc.constraint_object_id = fk.[object_id]
ORDER BY fkc.constraint_column_id
FOR XML PATH(N''), TYPE).value(N'.[1]', N'nvarchar(max)'),1,1,N'') + ');'
FROM sys.foreign_keys AS fk
INNER JOIN sys.tables AS rt -- referenced table
ON fk.referenced_object_id = rt.[object_id]
INNER JOIN sys.schemas AS rs
ON rt.[schema_id] = rs.[schema_id]
INNER JOIN sys.tables AS ct -- constraint table
ON fk.parent_object_id = ct.[object_id]
INNER JOIN sys.schemas AS cs
ON ct.[schema_id] = cs.[schema_id]
WHERE rt.is_ms_shipped = 0 AND ct.is_ms_shipped = 0
AND delete_referential_action_desc <> 'NO_ACTION' -- here
AND cs.name = 'datasets';
print(#drop);
print(#create);
-- ...
DBFiddle Demo
One warning! Please avoid adding ORDER BY.
This script uses
SELECT #drop += N'...'
<=>
SELECT #drop = #drop + N'...'
and it may start producing incorrect results. More nvarchar concatenation / index / nvarchar(max) inexplicable behavior