retrieving all Foreign Keys and their records - sql

Question

What I'm trying to achieve is the following.
When I delete a record I want to check if there are any FK relationships and it needs to be recursive. That way I can display a list of all records that are related to the one you want to delete.
So a small example of nested links
project 1 -> phase 1 -> block 1 -> ..
So when I try to delete project 1 I need to get a list of the items you need to delete first:
phase 1
block 1
....
I wanted to do this with a stored procedure that takes an ID and a tablename (format [chema].[tablename]) and finds all these linked records.
The problem I'm having is with the recursive part.
Here's my code so far:
ALTER PROCEDURE core.usp_CanBeDeleted
#entityId int,
#entityName nvarchar(250)
AS
BEGIN
DECLARE #NumberRecords int, #RowCount int
DECLARE #childId int
DECLARE #query nvarchar(max)
DECLARE #eName nvarchar(250) , #keyName nvarchar(250)
DECLARE #columnName nvarchar(250)
DECLARE #keys TABLE(
RowID int IDENTITY(1, 1),
name nvarchar(250),
entityName nvarchar(250),
columnName nvarchar(250)
)
if not exists (select * from sysobjects where name='partialResults' and xtype='U')
BEGIN
CREATE TABLE partialResults(
RowID int IDENTITY(1, 1),
id int,
parentId int,
name nvarchar(250),
FK_name nvarchar(250)
)
END
DECLARE #recusiveResults TABLE(
RowID int,
id int,
parentId int,
name nvarchar(250),
FK_name nvarchar(250)
)
DECLARE #results TABLE(
RowID int,
id int,
parentId int,
name nvarchar(250),
FK_name nvarchar(250)
)
SET #RowCount = 1
-- get all FK's of the entity
INSERT INTO #keys
SELECT name, '[' + OBJECT_SCHEMA_NAME(parent_object_id) + '].[' + OBJECT_NAME(parent_object_id)+ ']',cu.column_name
from sys.foreign_keys k
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU
ON k.name = CU.CONSTRAINT_NAME
where k.referenced_object_id = OBJECT_ID(#entityName)
-- set variable to number of records in temp table
SET #NumberRecords = ##ROWCOUNT
-- loop through the FK's an get all linked entities
WHILE(#RowCount <= #NumberRecords)
BEGIN
SELECT #keyName = name, #eName = entityName, #columnName = columnName
FROM #keys
WHERE RowId = #RowCount
-- get all FK information
SET #query = 'INSERT INTO partialResults(FK_name, name, id, parentId)'
+ ' SELECT ''' + #keyName + ''','''+ #eName + ''',' + 'id,' + cast(#entityId as varchar(25)) + ' as parentid'
+ ' FROM ' +#eName
+ ' WHERE id in '
+ ' (SELECT ' + #columnName
+ ' FROM ' + #entityName
+ ' WHERE id = ' + cast(#entityId as varchar(25))
+ ' )'
--print #query
EXEC (#query)
SET #RowCount = #RowCount + 1
END
-- rest number of records
SET #RowCount = 1
SELECT #NumberRecords = count(id)
FROM partialResults
-- save partialResults
INSERT INTO #results--(FK_name, name, id, parentId)
SELECT *--FK_name, name, id, parentId
FROM partialResults
DELETE FROM partialResults
WHILE(#RowCount <= #NumberRecords)
BEGIN
-- select next row
SELECT #childId = id, #eName = name
FROM #results
WHERE RowId = #RowCount
INSERT INTO #recusiveResults
EXEC core.usp_CanBeDeleted #childId, #eName
SET #RowCount = #RowCount + 1
END
INSERT INTO #results
SELECT *
FROM #recusiveResults
if exists (select * from sysobjects where name='partialResults' and xtype='U')
BEGIN
-- remove temp tables
DROP TABLE partialResults
END
-- return results
SELECT *
FROM #results
END
GO
the problem lies here:
INSERT INTO #recusiveResults
EXEC core.usp_CanBeDeleted #childId, #eName
Apparantly you can't nest an insert exec.
however I don't really see any other way to do it.
I've tried converting it into a function but then there are other problems like the dynamic query.
Any help would be greatly apreciated.

Answer 1

Split the procedure into an outer and an inner procedure.
In the outer procedure create a #results temp-table and then call the inner procedure.
In the inner procedure put all the logic including the recursion, but instead of selecting out the result at the end insert the result into the already existing #results table.
That way you safe a lot of time because you dont have to move data around as much. You also don't have to nest INSERT...EXEC anymore.
You also don't need the dbo.PartialResults table anymore as you can write directly into the #results table within the dynamic statement. If you still need it, to make the recursion work replace it with a #partialResults temp table that you create in the inner procedure (DON'T check for existence, just create the new one. See http://sqlity.net/en/1109/temp-tables-scoping-eclipsing/ for an explanation of temp table scoping). That way each execution is creating its own temp table and you don't have to deal with the clean-up. This is also a little less heavy compared to using a real table.
Finally, all the table variables can go too.
At the end of the inner procedure you can then do a simple SELECT * FROM #results; to output all the collected results.