How to use NULL or empty string in SQL

How to use NULL or empty string in SQL

sql sql-server null where

sql-server

SQL : BETWEEN vs <= and >=

sql sql-server tsql where between

sql-server

SQL Server: Multiple table joins with a WHERE clause

sql-server join where

sql-server

Invalid column name error in WHERE clause, column selected with CASE

sql-server tsql case where calculated-columns

sql-server

Why can't I use filter my WHERE clause on a CASE statement column in SQL Server? [duplicate]

sql sql-server case where

sql-server