Group_Concat 在子查询中删除重复项

Question

我们的数据库中有几个重复的商店需要删除，我们通过使用商店的纬度来识别重复的商店。

在生产者 table 的这个示例中，我们想要删除生产者 ID 123（我们的生产 Table 有 10K 行）。

+------+--------+------+------+---------+--------+
| producerID  | producerName  | type    | lat    |
+------+--------+------+------+---------|--------|
|  123        | ToysRUs       |  Retail | 52.445 |     
|  124        | Toys R Us     |  Online | 52.445 |
|  234        | GameStop      |  Retail | 55.150 |
|  345        | Amazon        |  Online | 56.110 |
+------+--------+------+------+---------+--------|

*Store 与 Producer 相同

此查询为我们提供了具有相同纬度值的所有生产者 ID。

SELECT COUNT(*) AS 'TotalStores', GROUP_CONCAT(producerID, SEPARATOR ',') AS 'DupeStores'
FROM Producer 
GROUP BY lat 
HAVING TotalStores > 1
ORDER BY TotalStores DESC

+------+--------+------+----+
| TotalStores | DupeStores  |
+------+--------+------+----+
|  3          | 123,124,125 |
|  3          | 555,556,557 |
|  2          | 666,665     |
|  2          | 777,787     |
+------+--------+------+----+

然后，我们使用这些生产者 ID (copy/paste) 和运行另一个查询来根据类型删除那些重复项。任何具有重复且类型为 'Retail' 的内容，我们都想删除。

DELETE FROM Producer WHERE type = 'Retail'
AND storeID IN (123, 124, 125, 555, 556, 557, 666, 665, 777, 787)

我们如何将这些组合成一个查询？当我尝试这样做时，出现错误：

Operand should contain 1 column(s)

DELETE FROM Producer WHERE type = 'Retail'
AND producerID IN (SELECT COUNT(*) AS 'TotalStores', GROUP_CONCAT(producerID SEPARATOR ',')
FROM Producer 
GROUP BY lat 
HAVING TotalStores > 1)

Answer 1

在 DELETE 语句中使用自联接：

DELETE p1
FROM Producer p1 INNER JOIN Producer p2 
ON p2.lat = p1.lat 
WHERE p1.type = 'Retail' AND p2.type <> p1.type

参见demo。

Group_Concat 在子查询中删除重复项

Group_Concat in Subquery to Remove Duplicates

mysql

subquery

duplicates