case when

SELECT
id,
CASE
WHEN sale_rank = 0 THEN
"LV0"
WHEN sale_rank = 1 THEN
"LV1"
WHEN sale_rank = 2 THEN
"LV2"
WHEN sale_rank = 3 THEN
"LV3"
WHEN sale_rank = 4 THEN
"LV4"
WHEN sale_rank = 5 THEN
"LV5"
WHEN sale_rank = 6 THEN
"LV6"
ELSE ‘wrong‘

END as sale_rank
FROM
users
LIMIT 100;

原文：http://www.cnblogs.com/php-linux/p/7995155.html