SQL - Cascading Delete, Or Delete Trigger, Maintaining Referential Integrity - PLEASE HELP ME!!!

Nov 13, 2006

I am having great difficulty with cascading deletes, delete triggers and referential integrity.

The database is in First Normal Form.

I have some tables that are child tables with two foreign keyes to two different parent tables, for example:

Table A
/
Table B Table C
/
Table D

So if I try to turn on cascading deletes for A/B, A/C, B/D and C/D relationships, I get an error that I cannot have cascading delete because it would create multiple cascade paths. I do understand why this is happening. If I delete a row in Table A, I want it to delete child rows in Table B and table C, and then child rows in table D as well. But if I delete a row in Table C, I want it to delete child rows in Table D, and if I delete a row in Table B, I want it to also delete child rows in Table D.

SQL sees this as cyclical, because if I delete a row in table A, both table B and table C would try to delete their child rows in table D.

Ok, so I thought, no biggie, I'll just use delete triggers. So I created delete triggers that will delete child rows in table B and table C when deleting a row in table A. Then I created triggers in both Table B and Table C that would delete child rows in Table D.

When I try to delete a row in table A, B or C, I get the error "Delete Statement Conflicted with COLUMN REFERENCE". This does not make sense to me, can anyone explain? I have a trigger in place that should be deleting the child rows before it attempts to delete the parent row...isn't that the whole point of delete triggers?????

This is an example of my delete trigger:

CREATE TRIGGER [DeleteA] ON A
FOR DELETE
AS
Delete from B where MeetingID = ID;
Delete from C where MeetingID = ID;

And then Table B and C both have delete triggers to delete child rows in table D. But it never gets to that point, none of the triggers execute because the above error happens first.

So if I then go into the relationships, and deselect the option for "Enforce relationship for INSERTs and UPDATEs" these triggers all work just fine. Only problem is that now I have no referential integrity and I can simply create unrestrained child rows that do not reference actual foreign keys in the parent table.

So the question is, how do I maintain referential integrity and also have the database delete child rows, keeping in mind that the cascading deletes will not work because of the multiple cascade paths (which are certainly required).

Hope this makes sense...
Thanks,
Josh


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while also deleting any child/grandchild records and so on. This is designed to do the
same sort of thing as Access's cascade delete function. It first reads the sysforeignkeys
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*/
(
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@cCriteria nvarchar(1000), /* criteria used to delete the rows required */
@iRowsAffected int OUTPUT /* number of records affected by the delete */
)
As
set nocount on
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@cCol varchar(255), /* name of the linking field on the child table */
@cRefTab varchar(255), /* name of the parent table */
@cRefCol varchar(255), /* name of the linking field in the parent table */
@cFKName varchar(255), /* name of the foreign key */
@cSQL nvarchar(1000), /* query string passed to the sp_ExecuteSQL procedure */
@cChildCriteria nvarchar(1000), /* criteria to be used to delete
records from the child table */
@iChildRows int /* number of rows deleted from the child table */

/* declare the cursor containing the foreign key constraint information */
DECLARE cFKey CURSOR LOCAL FOR
SELECT SO1.name AS Tab,
SC1.name AS Col,
SO2.name AS RefTab,
SC2.name AS RefCol,
FO.name AS FKName
FROM dbo.sysforeignkeys FK
INNER JOIN dbo.syscolumns SC1 ON FK.fkeyid = SC1.id
AND FK.fkey = SC1.colid
INNER JOIN dbo.syscolumns SC2 ON FK.rkeyid = SC2.id
AND FK.rkey = SC2.colid
INNER JOIN dbo.sysobjects SO1 ON FK.fkeyid = SO1.id
INNER JOIN dbo.sysobjects SO2 ON FK.rkeyid = SO2.id
INNER JOIN dbo.sysobjects FO ON FK.constid = FO.id
WHERE SO2.Name = @cTableName

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BEGIN
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recursive calls */
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@cRefTab +'] WHERE ' + @cCriteria + ')'
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END
Close cFKey
DeAllocate cFKey
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print @cSQL
EXEC sp_ExecuteSQL @cSQL
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--------
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Server: Msg 217, Level 16, State 1, Procedure spDeleteRows, Line 58
Maximum stored procedure, function, trigger, or view nesting level exceeded (limit 32).

Can anyone out there suggest a better way of implementing on a database without a limitation of levels.. we are talking about a HUGE DB with lots of table and FK referentials..

Please advice.. or solve the problem..
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(
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@Table NVARCHAR(128) = NULL
)
RETURNS@Return TABLE
(
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)
AS
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(
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[Schema] NVARCHAR(128) NOT NULL,
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HasPk TINYINT NOT NULL
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Indent,
[Catalog],
[Schema],
[Table],
[Column],
pkCatalog,
pkSchema,
pkTable,
pkColumn,
pkType,
pkSize,
IsSelfJoin,
HasPk
)
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Indent,
[Catalog],
[Schema],
[Table],
[Column],
pkCatalog,
pkSchema,
pkTable,
pkColumn,
pkType,
pkSize,
SelfJoin,
CASE
WHEN [Column] IS NULL THEN 0
ELSE 1
END
FROMdbo.fnTableTree(@Schema, @Table)

IF @@ROWCOUNT = 0
RETURN

DECLARE@SQL TABLE
(
ID INT IDENTITY(1, 1),
RowID INT PRIMARY KEY CLUSTERED,
IsSelfJoin TINYINT NOT NULL,
HasPk TINYINT NOT NULL,
[SQL] NVARCHAR(4000) NOT NULL
)

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@ID INT,
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@RowSQL NVARCHAR(4000),
@EndSQL NVARCHAR(4000),
@pkColumn NVARCHAR(128),
@IsSelfJoin TINYINT,
@HasPk TINYINT

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(
RowID INT NOT NULL,
StepID INT IDENTITY(0, 1) PRIMARY KEY NONCLUSTERED,
[SQL] NVARCHAR(4000)
)

WHILE NOT EXISTS (SELECT * FROM @SQL WHERE RowID = 1)
BEGIN
SELECT TOP 1@RowID = c.RowID,
@ID = c.RowID,
@Indent = c.Indent,
@TSQL = N'',
@EndSQL = N'',
@IsSelfJoin = c.IsSelfjoin,
@HasPk = c.HasPk
FROM@Constraints AS c
LEFT JOIN@SQL AS s ON s.RowID = c.RowID
WHEREs.RowID IS NULL
ORDER BYc.Indent DESC,
c.RowID DESC

WHILE @ID > 0
BEGIN
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@EndSQL = N' WHERE t' + CAST(@ID AS NVARCHAR(12)) + '.' + QUOTENAME(COALESCE(c.[Column], '%0')) + N' = ''%1''',
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FROM@Constraints AS c
WHEREc.RowID = @ID
ELSE
SELECT@RowSQL = N' INNER JOIN ' + QUOTENAME(c.[Catalog]) + N'.' + QUOTENAME(c.[Schema]) + N'.' + QUOTENAME(c.[Table]),
@RowSQL = @RowSQL + N' AS t' + CAST(@ID AS NVARCHAR(12)) + N' ON t' + CAST(@ID AS NVARCHAR(12)) + N'.' + QUOTENAME(c.[Column]),
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@IsSelfJoin = @IsSelfJoin | c.IsSelfJoin
FROM@Constraints AS c
WHEREc.RowID = @ID

SELECT TOP 1@ID = c.RowID,
@Indent = c.Indent,
@RowSQL = @RowSQL + N' = t' + CAST(c.RowID AS NVARCHAR(12)) + N'.' + @pkColumn,
@IsSelfJoin = @IsSelfJoin | c.IsSelfJoin
FROM@Constraints AS c
WHEREc.RowID < @ID
AND c.Indent < @Indent
ORDER BYc.Indent DESC,
c.RowID DESC

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SET@ID = 0

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END

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(
RowID,
IsSelfJoin,
HasPk,
[SQL]
)
VALUES(
@RowID,
@IsSelfJoin,
@HasPk,
@TSQL + @EndSQL
)

IF @IsSelfJoin = 1
BEGIN
DECLARE@Yak NVARCHAR(160),
@Catalog NVARCHAR(128),
@Column NVARCHAR(128)

SELECT@Yak = pkType + COALESCE('(' + CAST(pkSize AS NVARCHAR(12)) + ')', ''),
@Catalog = [Catalog],
@Schema = [Schema],
@Table = [Table],
@Column = [Column],
@Catalog = [Catalog],
@Table = [Table],
@pkColumn = pkColumn
FROM@Constraints
WHERERowID = @RowID

SET@RowSQL = 'DECLARE@Lvl INT
SET@Lvl = 0
DECLARE@Stage TABLE (RowID INT IDENTITY(0, 1), Lvl INT, RowKey ' + @Yak + ')
INSERT @Stage (Lvl, RowKey) '
+ REPLACE(@TSQL + @EndSQL, 'DELETE t' + CAST(@RowID AS NVARCHAR(12)) + '', 'SELECT 0, t' + CAST(@RowID AS NVARCHAR(12)) + '.' + QUOTENAME(@Column) + '')
+ ' WHILE @@ROWCOUNT > 0
BEGIN
SET@Lvl = @Lvl + 1

INSERT@Stage (Lvl, RowKey)
SELECT@Lvl,
t.' + QUOTENAME(@pkColumn) + '
FROM' + QUOTENAME(@Catalog) + '.' + QUOTENAME(@Schema) + '.' + QUOTENAME(@Table) + ' AS t
INNER JOIN@Stage AS s ON s.RowKey = t.' + QUOTENAME(@Column) + '
AND s.Lvl = @Lvl - 1
LEFT JOIN@Stage AS cr ON cr.RowKey = t.' + QUOTENAME(@pkColumn) + '
WHEREcr.RowKey IS NULL
END
SELECT ''DELETE FROM ' + QUOTENAME(@Catalog) + '.' + QUOTENAME(@Schema) + '.' + QUOTENAME(@Table) + ' WHERE ' + QUOTENAME(@pkColumn) + ' = '' + QUOTENAME(RowKey, '''''''')
FROM @Stage
WHERE RowID > 0
ORDER BY RowID DESC'

INSERT@Unwind
(
RowID,
[SQL]
)
VALUES(
@RowID,
@RowSQL
)
END
END

INSERT@Return
(
RowID,
IsSelfJoin,
HasPk,
[SQL]
)
SELECTs.ID,
s.IsSelfJoin,
s.HasPk,
CASE
WHEN u.RowID IS NULL THEN s.[SQL]
ELSE u.[SQL]
END
FROM@SQL AS s
LEFT JOIN@Unwind AS u ON u.RowID = s.RowID
ORDER BYs.ID,
u.StepID

RETURN
ENDE 12°55'05.25"
N 56°04'39.16"

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InsuranceCompany

Which works great, and enables me to query all basic job details from one table (JobDetails) rather than multiple tables for every job type.

BUT: I don't know how to enforce the referential integrity of the database. Obviously I can use a constraint to cascade deletes from the PropertyDetails table to the JobDetails table through the PropertyID, but there doesn't appear to then cascade the deletes from the JobDetails table to the individual Job tables as JobDetails has no idea what tables are there.

If I store the relevant individual table name as the JobType in the JobDetails table, could I use a trigger to somehow delete the related record from that table?

Littlecharva

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Disabling Referential Integrity Database-wide On Import

Apr 10, 2006

Is there a way to disable referential integrity on all destination tables for an import?
Thanks.

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