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How to check for null value in trigger?

I have a Table (Tbl_1) into which a record is inserted from time to time. Once a record is inserted into Tbl_1 then I will have to use the columns from the new record and populate other tables. The column values in Tbl_1 can be "NULL". I am planning to write a DB Trigger to take care of creating records in other tables. I am not sure how I can handle existence of "NULL" column values. If a column value is NULL then I will will have to insert "NULL" value.  What is the conditional statement I can make use of to check for "NULL" value? Any help is very much appreciated.

Kind regards
0
samble
Asked:
samble
1 Solution
 
Anthony PerkinsCommented:
>>What is the conditional statement I can make use of to check for "NULL" value?<<

Where ColumnName Is Null

Or
Where ColumnName Is Not Null
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crescendoCommented:
To be more precise,

  WHERE inserted.ColumnName IS NULL

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sambleAuthor Commented:
Thanks for the quick response. The issue is I have to check on multiple columns and my SQL statement will be subject to the condition. Just for example if I have four columns then depending on the value of each column the SQL statement will have to be different. Potentially I can have upto 16 different SQL statements. Do you agree with this?

Kind regards
0
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Anthony PerkinsCommented:
>>Do you agree with this?<<
Without seeing your SQL statement it is a littel difficult to hazard a guess.  But in general I would say no, it is not necessary.
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Anthony PerkinsCommented:
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Thanks.
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hkamalCommented:
samble, a trigger is effectively a proc attached to a table, you can easily create a conditional dynamic sql
viz:

CREATE TABLE Customers (CustomerName VARCHAR(100) NULL, CustomerAge INT NULL, ....)
GO
                 
CREATE TRIGGER cust_insert
ON Customers
FOR INSERT AS
DECLARE @sql=varchar(255)
SELECT @sql="insert TableA (col1) select "+CASE WHEN CustomerName = NULL THEN "NULL" ELSE CustomerName  END
SELECT @sql=@sql+"insert TableB (col1) select "+CASE WHEN CustomerAge = NULL THEN "NULL" ELSE CustomerAge  END
..
..
EXEC (@sql)
GO

INSERT Customers SELECT "George W Bush", 99
SELECT * FROM Customers


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Anthony PerkinsCommented:
I afraid this:
CASE WHEN CustomerName = NULL

Will never be true.

You cannot compare to a Null using an equal sign.

To see what I mean, try this from Query Analyzer:
If Null = Null
   Select 'Null = Null'
Else
   Select 'Null <> Null'
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sambleAuthor Commented:
You are right about your observation. I will have to use "IS NULL" operator to compare. Despite this flaw the logic is generally okay unless of course I am totally wrong here.

Kind regards
0
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