sql check if null or empty code example

Example 1: t sql null or empty string

select * from vendor
where isnull(vendor_email,'') = ''

Example 2: sql check for null and empty string

IF ISNULL(@param) OR @param = '' THEN doSomething...

Example 3: sql if empty then

SELECT COALESCE(NULLIF(SomeColumn,''), ReplacementColumn)
FROM SomeTable