The Singleton SELECT statement is used to return a single row from a query operation. 

SELECT <expression> (, ...)
 INTO <name> [, ...]
 FROM <select_statement>

where:

expression
is an expression that is evaluated to determine the row to return.
name
is the identifier of the object in which to update with the row returned .
select_statement
is a SELECT statement that is used to select the data containing the row to be returned.
Note: The SELECT should return 0 rows if not updating or one row to update. Returning more than one row returns an exception.