if then (SQL statement) else (SQL statement 2)

[Roy Wasse]

Hi,
I'm trying to use an if then alike statement in MySQL, myabe anyone can tell me the 
correct syntax
if got a variable named naam. when the content of this variables is empty the 
following SQL statement should be executed:
select * from beheerder;
when naam is not empty:
select * from beheerder wherer naam like '%naam%'
Can this be done with SQL language?

thank you,

Roy