sql 语法有什么问题

Question

SELECT 
    a.Name, a.About, 
    COUNT(b.Id) AS TotalCities, 
    SUM(b.NoOfDwellers) AS TotalCityDwellers 
FROM 
    Countries a 
LEFT JOIN 
    Cities b ON a.Id = b.CountryId 
WHERE 
    a.Name LIKE '%some str%'  
GROUP BY 
    a.Id 
ORDER BY 
    a.Name ASC

这个SQLreturns错误：

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

Answer 1

如果您有一个带有 GROUP BY 子句的 SELECT，则 SELECT 列列表中的每一列都必须一个聚合（SUM、COUNT、MAX 等），或者它必须在 GROUP BY 子句中。

您的 SELECT 列表中的 a.Name 和 a.About 均未由聚合处理 - 因此，这两列必须出现在 GROUP BY 子句中

SELECT 
    a.Name, a.About, 
    COUNT(b.Id) AS TotalCities, 
    SUM(b.NoOfDwellers) AS TotalCityDwellers 
FROM 
    Countries a 
LEFT JOIN 
    Cities b ON a.Id = b.CountryId 
WHERE 
    a.Name LIKE '%some str%'  
GROUP BY 
    a.Id, a.About, a.Name 
ORDER BY 
    a.Name ASC

Answer 2

在包含 group by 子句的查询中，结果中的每一行都代表整组行，这些行共享它们作为分组依据的列的相同值。因此，您 select 的每个项目都必须是这些列之一、对它们的 row-based 操作或聚合函数。您似乎在尝试根据 a 的 name 和 about 来汇总 b 的值。如果这是真的，您应该相应地修改您的 group by 子句：

SELECT 
    a.Name, a.About, 
    COUNT(b.Id) AS TotalCities, 
    SUM(b.NoOfDwellers) AS TotalCityDwellers 
FROM 
    Countries a 
LEFT JOIN 
    Cities b ON a.Id = b.CountryId 
WHERE 
    a.Name IS NULL 
GROUP BY 
    a.Name, a.About -- here!
ORDER BY 
    a.Name ASC

sql 语法有什么问题

What is the wrong with the sql syntax

sql

sql-server

select

syntax-error

sql-server-2012