Variables are a specific form of named memory region that can be used to store data. Depending on the agenda, the value of the program can be adjusted or Varied. In SQL, there are several different sorts of variables. Local variables are variables that are unique to a single SQL statement. They are defined within the statement and are used to store values that are specific to that statement only. Session variables are used to hold values that are used by several SQL statements at the same time. They are declared at the start of the session and are accessible to all SQL statements run during that time. The SQL engine uses system variables to store values. They are not specific to any SQL statement and are defined and set by the SQL engine.