查找重复的连接值

Question

我正在尝试在 MySQL 数据库中查找包含重复项的每一行。

1   alex    smith
2   bob     smith
3   alex    smith

我想return:

1   alex    smith
3   alex    smith

此代码将查找重复项，但不会列出重复的每一行。

SELECT
    *,
    CONCAT(`firstName`, ' ', `lastName`) as full_name,
    COUNT(*) d
FROM users
GROUP BY full_name
HAVING d > 1;

下面的代码是我试图获取重复的每一行的代码，但我收到错误“#1054 - 'IN/ALL/ANY subquery' 中的未知列 'full_name'”

SELECT CONCAT(`firstName`, ' ', `lastName`) as full_name
FROM users
WHERE full_name IN (
    SELECT CONCAT(`firstName`, ' ', `lastName`) as full_name
    FROM users
    GROUP BY full_name
    HAVING COUNT(full_name) > 1
)

Answer 1

您不能在 WHERE 子句中使用别名；而且您实际上并不需要 CONCAT （在这种情况下它会增加您的计算成本）；相反，您可以比较 "tuples".

SELECT *
FROM users
WHERE (`firstName`, `lastName`) IN (
    SELECT `firstName`, `lastName`
    FROM users
    GROUP BY `firstName`, `lastName`
    HAVING COUNT(*) > 1
);

查找重复的连接值

Find duplicate concat values

mysql

group-by

having