子查询
SELECT COUNT(*)
FROM (SELECT DISTINCT id
FROM tb1
) AS tb
单一查询
下面的语句只返回相同记录多于一条的ID
SELECT id
, COUNT()
FROM tb1
GROUP BY id
HAVING COUNT() > 1
子查询
SELECT COUNT(*)
FROM (SELECT DISTINCT id
FROM tb1
) AS tb
单一查询
下面的语句只返回相同记录多于一条的ID
SELECT id
, COUNT()
FROM tb1
GROUP BY id
HAVING COUNT() > 1