Question

表：

locations
---------
contract_id INT
order_position INT   # I want to find any bad data in this column

我想在给定的order_position中找到任何重复的contract_id。

因此，例如，如果两个locations行的contract_id “24845”并且两者都有order_position “3 ”

我正在使用MySQL 5.1。

Answer 1

select contract_id, order_position
from locations
group by contract_id, order_position
having count(*) > 1

Answer 2

SELECT contract_id, order_position, count(*)
FROM locations
GROUP BY contract_id, order_position
HAVING count(*) > 1

Answer 3

HAVING子句可以显示存在重复项的实例：

SELECT *
FROM locations
GROUP BY contract_id, order_position
HAVING COUNT(*) > 1

Answer 4

SELECT contract_id, order_position, COUNT(order_position) AS cnt
FROM locations
GROUP BY contract_id, order_position
HAVING cnt > 1;