Question

I have a table [MyTable] with a column [MyColumn] NVarchar(50). I have a nonclustered index on this column, now while running the below two queries:

SELECT  1
FROM    [MyTable] M
WHERE   M.[MyColumn] = @MyColumn

SELECT  1
FROM    [MyTable] M
WHERE   M.[MyColumn] = COALESCE(@MyColumn, M.[MyColumn] )   

I noticed the first query is using Index Seek (NonClustered) and the second one is using Index Scan (Non Clustered). May I know how will I make use of index seek with coalesce or isnull ?

Answer 1

May I know how will I make use of
index seek with coalesce or isnull ?

Perhaps not an answer to your question but you can have two different queries. One for the case where @MyColumn is null and one for the case where you want to use @MyColumn in the where clause.

IF @MyColumn IS NULL
BEGIN
  SELECT  1
  FROM    [MyTable] M
END  
ELSE
BEGIN
  SELECT  1
  FROM    [MyTable] M
  WHERE   M.[MyColumn] = @MyColumn
END