Question

我尝试设置左连接，但是当我使用一列group by并选择多列时，我遇到了SQL错误。

这是我的疑问：

SELECT
    b.ClientCode,
    b.LastName, b.FirstName,
    b."Id" AS IdClient,
    c.CaseDate,
    b.Gender,
    b.BirthDate
FROM
    dbo.Clients b
LEFT JOIN
    dbo.ClientCases c ON c.ClientCode = b.ClientCode
WHERE
    b.ClientCode LIKE '%1%'
    AND DATEDIFF(DAY, '01/06/2017', c.CaseDate) >= 0
    AND DATEDIFF(DAY, '05/06/2017', c.CaseDate) <= 0
GROUP BY
    b.ClientCode
ORDER BY
    b.ClientCode

当我写这样的查询时：

SELECT
    b.ClientCode,
    b.LastName, b.FirstName,
    b."Id" AS IdClient,
    c.CaseDate,
    b.Gender,
    b.BirthDate
FROM
    dbo.Clients b
LEFT JOIN
    dbo.ClientCases c ON c.ClientCode = b.ClientCode
WHERE
    b.ClientCode LIKE '%1%'
    AND DATEDIFF(DAY, '01/06/2017', c.CaseDate) >= 0
    AND DATEDIFF(DAY, '05/06/2017', c.CaseDate) <= 0
GROUP BY
    b.ClientCode, b.LastName, b.FirstName, b."Id",
    b.Gender, b.BirthDate, c.CaseDate
ORDER BY
    b.ClientCode

它正在运作 - 但它会返回重复的ClientCode ...

我该怎么办？

Answer 1

由于GROUP BY，您需要为其他列添加MAX（或MIN或其他聚合函数）。否则它不知道你想要的值。

SELECT b.ClientCode
    ,MAX(b.LastName)
    ,MAX(b.FirstName)
    ,MAX(b."Id") AS IdClient
    ,MAX(c.CaseDate)
    ,MAX(b.Gender)
    ,MAX(b.BirthDate)
FROM dbo.Clients b
LEFT JOIN dbo.ClientCases c ON c.ClientCode = b.ClientCode
WHERE b.ClientCode LIKE '%1%'
    AND DATEDIFF(day, '01/06/2017', c.CaseDate) >= 0
    AND DATEDIFF(day, '05/06/2017', c.CaseDate) <= 0
GROUP BY b.ClientCode
ORDER BY b.ClientCode

我怀疑你得到的错误是：

Msg 8120, Level 16, State 1, Line 1
Column 'blah blah' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

SQL Server：GROUP BY有一列

1 个答案: