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--general function if null then ''
ISNULL(the_field, '')
--with NULLIF check for empty field
ISNULL(NULLIF(the_field,''), '')
--select all records that is not null or empty
SELECT TOP 100 * FROM table WHERE ISNULL(NULLIF(the_field,'' ),NULL) IS NOT NULL ORDER BY 1 DESC
--Comparing NULLIF and CASE
USE AdventureWorks2008R2;
GO
SELECT ProductID, MakeFlag, FinishedGoodsFlag,
NULLIF(MakeFlag,FinishedGoodsFlag)AS 'Null if Equal'
FROM Production.Product
WHERE ProductID < 10;
GO
SELECT ProductID, MakeFlag, FinishedGoodsFlag,'Null if Equal' =
CASE
WHEN MakeFlag = FinishedGoodsFlag THEN NULL
ELSE MakeFlag
END
FROM Production.Product
WHERE ProductID < 10;
GO
src - https://docs.microsoft.com/en-us/previous-versions/sql/sql-server-2008-r2/ms177562(v=sql.105)
origin - https://www.pipiscrew.com/?p=18456 isnull-with-nullif-to-avoid-empty-string