SQL Stored Procedure with Input parameters with While loop - sql-server

Question

I have a code below that should insert records into the table but unfortunately this code foes not work in case multiple records are inserted or updated or deleted. How should I rewrite the code for procedure to loop through all the inserted / deleted records? And I do need to use that stored procedure with Input parameters (not just simple insert into ... select ... from ...)
IF EXISTS (SELECT * FROM MyDB.sys.triggers WHERE object_id = OBJECT_ID(N'[dbo].[MyTable_DEL_UPD_INS]'))
DROP TRIGGER [dbo].[MyTable_DEL_UPD_INS]
GO
CREATE TRIGGER [dbo].[MyTable_DEL_UPD_INS]
ON [MyDB].[dbo].[MyTable]
AFTER DELETE, UPDATE, INSERT
NOT FOR REPLICATION
AS
BEGIN
DECLARE #PKId INT,
#Code VARCHAR(5),
#AuditType VARCHAR(10)
SET #Code = 'TEST'
IF EXISTS (SELECT * FROM deleted d)
AND NOT EXISTS (SELECT * FROM inserted i)
BEGIN
SELECT TOP 1
#PKId = d.[MyTable_PK],
#AuditType = 'DELETE'
FROM
deleted d WITH (NOLOCK)
IF #PKId IS NOT NULL
AND #Code IS NOT NULL
EXEC MyDB.[dbo].[SP_Audit] #PKId, #Code, #AuditType
END
IF EXISTS (SELECT * FROM deleted d)
AND EXISTS (SELECT * FROM inserted i)
BEGIN
SELECT TOP 1
#PKId = d.[MyTable_PK],
#AuditType = 'UPDATE'
FROM
deleted d WITH (NOLOCK)
IF #PKId IS NOT NULL
AND #Code IS NOT NULL
EXEC MyDB.[dbo].[SP_Audit] #PKId, #Code, #AuditType
END
IF NOT EXISTS (SELECT * FROM deleted d)
AND EXISTS (SELECT * FROM inserted i)
BEGIN
SELECT TOP 1
#PKId = d.[MyTable_PK],
#AuditType = 'INSERT'
FROM
deleted d WITH (NOLOCK)
IF #PKId IS NOT NULL
AND #Code IS NOT NULL
EXEC MyDB.[dbo].[SP_Audit] #PKId, #Code, #AuditType
END
END
GO
ALTER TABLE [MyDB].[dbo].[MyTable] ENABLE TRIGGER [MyTable_DEL_UPD_INS]

Answer 1

You should avoid using loops in triggers.
Triggers should be as quick to run as possible, since SQL Server will not return control to whatever statement that fired the trigger until the trigger is completed.
So instead of a loop, you should modify your SP_Audit procedure to work with multiple records instead of a single one.
usually, this is easily be done using a table valued parameter.
If you could post the SP_Audit as well, we could give you a complete solution.
Since you didn't post it, you can use these guidelines as a start:
First, you create a user defined table type:
CREATE TYPE dbo.Ids AS TABLE
(
Id int NOT NULL PRIMARY KEY
)
GO
Then, you create the procedure to use it:
CREATE PROCEDURE [dbo].[STP_Audit_MultipleRecords]
(
#IDs dbo.Ids readonly,
#Code CHAR(4),
#AuditType CHAR(6)
)
AS
-- Implementation here
GO
Last, your write your trigger like this:
CREATE TRIGGER [dbo].[MyTable_DEL_UPD_INS]
ON [MyDB].[dbo].[MyTable]
AFTER DELETE, UPDATE, INSERT
NOT FOR REPLICATION
AS
BEGIN
DECLARE #HasDeleted bit = 0,
#HasInserted bit = 0,
#AuditType CHAR(6),
#Code CHAR(4)
SET #Code = 'TEST'
DECLARE #IDs as dbo.Ids
IF EXISTS (SELECT * FROM deleted d)
SET #HasDeleted = 1
IF EXISTS (SELECT * FROM inserted i)
SET #HasInserted = 1
IF #HasDeleted = 1
BEGIN
IF #HasInserted = 1
BEGIN
SET #AuditType = 'UPDATE'
END
ELSE
BEGIN
SET #AuditType = 'DELETE'
END
END
ELSE
IF #HasInserted = 1
BEGIN
SET #AuditType = 'INSERT'
END
INSERT INTO #IDs (Id)
SELECT [MyTable_PK]
FROM inserted
UNION
SELECT [MyTable_PK]
FROM deleted
EXEC [dbo].[STP_Audit_MultipleRecords] #IDs, #Code, #AuditType
END
GO
Notes:
The #HasDeleted and #HasInserted variables are to allow you to only execute the EXISTS query once for every procedure.
Getting the primary key values from the deleted and inserted table is done using a single union query. Since union eliminates duplicate values, you can write this query just once. If you want to, you can write a different query for each audit type, but then you will have to repeat the same query 3 times (with different tables)
I've changed the data types of your #code and #AuditType variables to char, since they have a fixed length.