关于查询表中数据的问题

怎么用php查询出表中有重复的数据呢，如下图
2. 查询出下表sdb_b2c_cat_alias中alias有重复的数据

SELECT *
FROM (

SELECT COUNT(
alias) AS num, sdb_b2c_cat_alias. *
FROM sdb_b2c_cat_alias
WHERE 1
GROUP BY alias
) AS tmptable
WHERE tmptable.num >1

SELECT COUNT(1) as num,alias FROM sdb_b2c_cat_alias GROUP BY alias HAVING num >1