What is bad in this query ?

Hi,

What is bad in this query ?

SELECT CASE
WHEN EXIST(SELECT * FROM user WHERE name=rado)
THEN (INSERT INTO user VALUES('rado'))
END;

PostgreSQL return

ERROR: parser: parse error at or near "INTO"

table user have only one column 'name' .

Thanks

--
Rado Petrik <r(dot)p(at)szm(dot)sk>