How to debug a T-SQL trigger?

Question

I have a table t, which has an \"after insert\" trigger called trgInsAfter. Exactly how do i debug it? i\'m no expert on this, so the question and steps performed might look sil

Answer 1

For whatever reason I couldn't get @Damien_The_Unbeliever's solution to work. At least, not on a trigger attached to a table. When I did a Step Into it just executed the query every time without stepping into the trigger.

Then I noticed in the comments of that approach that you can't see any of the table values anyway.

So......

I ended up creating a generic Debug Table.

USE [Your_DB]
GO

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[Debug_Table](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [Name] [varchar](60) NOT NULL,
    [Value] [sql_variant] NULL,
    [Description] [varchar](max) NULL,
    [Captured] [datetime] NOT NULL
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

And then in my trigger I did something like this...

DECLARE @ItemNum nvarchar(128)
SELECT  @ItemNum = Item_Number FROM inserted

DECLARE @debugOn as bit = 1
-- Debug
    IF @debugOn = 1
    BEGIN
        INSERT INTO Debug_Table (Name, Value, Description, Captured)
        VALUES ( 'Item Number', @ItemNum, 'The item number from the inserted table in tr_VaultItemIterations_ZCode_Monitor.', GETDATE())
    END;
-- End Debug

After the trigger fired from the table I could view any of the variables I inserted to the Debug_Table.

After you're done debugging you could could easily turn off debugging inserts by changing the @debugOn variable to 0 in case you ever need to debug again in the future; or just remove the debug code altogether.