How to use NULL or empty string in SQL

Question

Select *
From Table
Where (col is null or col = '')

Or

Select *
From Table
Where IsNull(col, '') = ''

If you need it in SELECT section can use like this.

SELECT ct.ID, 
       ISNULL(NULLIF(ct.LaunchDate, ''), null) [LaunchDate]
FROM   [dbo].[CustomerTable] ct

You can replace the null with your substitution value.

You can simply do this:

SELECT *
FROM   yourTable
WHERE  yourColumn IS NULL OR yourColumn = ''

SELECT *
FROM   TableName
WHERE  columnNAme IS NULL OR 
       LTRIM(RTRIM(columnName)) = ''

To find rows where col is NULL, empty string or whitespace (spaces, tabs):

SELECT *
FROM table
WHERE ISNULL(LTRIM(RTRIM(col)),'')=''

To find rows where col is NOT NULL, empty string or whitespace (spaces, tabs):

SELECT *
FROM table
WHERE ISNULL(LTRIM(RTRIM(col)),'')<>''

Some sargable methods...

SELECT *
FROM #T
WHERE SomeCol = '' OR SomeCol IS NULL;

SELECT *
FROM #T
WHERE SomeCol = '' 
UNION ALL
SELECT *
FROM #T
WHERE  SomeCol IS NULL;

SELECT *
FROM #T
WHERE EXISTS ((SELECT NULL UNION SELECT '') INTERSECT SELECT SomeCol);

And some non-sargable ones...

SELECT *
FROM #T
WHERE IIF(SomeCol <> '',0,1) = 1;

SELECT *
FROM #T
WHERE NULLIF(SomeCol,'') IS NULL;

SELECT *
FROM #T
WHERE ISNULL(SomeCol,'') = '';