select
case boolean-expr
statements
[ case boolean-expr
statements ]
...
[ default
statements ]
Use a select statement to execute at most one case from a group.
Once the first boolean-expr in the list evaluates to TRUE, its statement is executed and then control passes to the first statement after the select statement.
If no boolean-expr evaluates to TRUE, and there is a default label, then control passes to the statement immediately following it. There can be only one default label, and it must be the last label.