Question

Dear all I´m having trouble with my trigger.

Am I doing this at all right, right now it only works for Insert. I think I´m pretty close tho please help me if you have the time. I´m trying to store all the inserts, updates and deletes into the table customers_changelog via trigger. There is something wrong with the code I cant delete or update customers I can only insert new ones. Please help my I have been spending plenty of hours on this and just cant get this to work! 🙂

create table customers (
customerid int identity primary key,
name varchar(100) not null,
address varchar(100)
)
go

create table customers_changelog (
customerid int,
name varchar(100) not null,
address varchar(100),
change_user varchar(32),
change_time datetime,
change_action char(1) default 'I',
check (change_action = 'I' or change_action = 'D')
)
go


CREATE TRIGGER log_changes
ON customers
AFTER INSERT, UPDATE, DELETE
AS 
BEGIN
    SET NOCOUNT ON;

--
-- Check if this is an INSERT, UPDATE or DELETE Action.
-- 
DECLARE @customerid1 as int;
DEClARE @name1 as varchar(32);
DECLARE @address1 as varchar(100);
DECLARE @change_action1 as char(1);
DECLARE @change_time1 as datetime;
DECLARE @change_user1 as varchar(32);

select  @customerid1 = c.customerid, @name1 = c.name, @address1 = c.address
from customers c, inserted i
where c.customerid = i.customerid 

SET @change_time1 = CURRENT_TIMESTAMP;
SET @change_user1 = CURRENT_USER;
INSERT INTO customers_changelog(customerid,name,address,change_action,change_time,change_user)
    VALUES(@customerid1,@name1,@address1,'I',@change_time1,@change_user1)
IF EXISTS(SELECT * FROM DELETED)
BEGIN    
            IF EXISTS(SELECT * FROM INSERTED) 
            INSERT INTO customers_changelog VALUES(@customerid1,@name1,@address1,'U',@change_time1,@change_user1)
            ELSE 
            INSERT INTO customers_changelog VALUES(@customerid1,@name1,@address1,'D',@change_time1,@change_user1)

END
ELSE 
    IF NOT EXISTS(SELECT * FROM INSERTED) RETURN;
END

Answer 1

Assuming MS-SQL from syntax – So couple issues here:
1. Need to specify column lists in the “update” and “delete” inserts because the column order in the table doesn’t match your inserts.
2. Can’t use “inserted” data for delete insert

ALTER TRIGGER [dbo].[log_changes] ON [dbo].[customers] AFTER INSERT, UPDATE, DELETE AS 
BEGIN
    SET NOCOUNT ON;
    DECLARE @customerid1 as int;
    DEClARE @name1 as varchar(32);
    DECLARE @address1 as varchar(100);
    DECLARE @change_action1 as char(1);
    DECLARE @change_time1 as datetime;
    DECLARE @change_user1 as varchar(32);

    select  @customerid1 = c.customerid, @name1 = c.name, @address1 = c.address
    from customers c, inserted i
    where c.customerid = i.customerid 

    SET @change_time1 = CURRENT_TIMESTAMP;
    SET @change_user1 = CURRENT_USER;

    IF EXISTS(SELECT * FROM DELETED)
    BEGIN    
                IF EXISTS(SELECT * FROM INSERTED) 
                INSERT INTO customers_changelog(customerid,name,address,change_action,change_time,change_user) 
                    VALUES(@customerid1,@name1,@address1,'U',@change_time1,@change_user1)
                ELSE 
                BEGIN
                    select  @customerid1 = d.customerid, @name1 = d.name, @address1 = d.address
                        from deleted d
                    INSERT INTO customers_changelog(customerid,name,address,change_action,change_time,change_user) 
                        VALUES(@customerid1,@name1,@address1,'D',@change_time1,@change_user1)
                END

    END
    ELSE
    BEGIN
        IF NOT EXISTS(SELECT * FROM INSERTED) RETURN;
        INSERT INTO customers_changelog(customerid,name,address,change_action,change_time,change_user)
            VALUES(@customerid1,@name1,@address1,'I',@change_time1,@change_user1) 
    END
END