Question

我在SQL Server中有一个数据库，列出包含每个事件日期的海事事件。对于图表说明，我现在想要编写一个SQL语句（对于Visual Studio），它给出了每年的事件总数。

示例：

2009 2010（年 - X轴）

4575 5432（年 - Y轴）

X轴的SELECT语句，我可以写成

SELECT year1, year2 FROM (SELECT 2009 AS year1) AS a, ( SELECT 2010 AS year2) AS b

但是第二个怎么样？当我写下这样的东西时：

SELECT totalyear1, totalyear2 FROM (SELECT COUNT(Reference) FROM STO.dbo.STOMaritimeIncidents WHERE [Incident date] = 2010 AS totalyear1) AS a, (SELECT COUNT(Reference) FROM STO.dbo.STOMaritimeIncidents WHERE [Incident date] = 2009 AS totalyear2) AS b

我得到错误，如“ Msg 156，Level 15，State 1，Line 1 关键字“AS”附近的语法不正确。“

如果有人能给我解释或帮助我，我真的很感激。非常感谢！

Answer 1

需要对列本身进行AS totalyear1和AS totalyear2别名声明：

SELECT totalyear1, totalyear2 
FROM (SELECT COUNT(Reference) AS totalyear1 
      FROM STO.dbo.STOMaritimeIncidents 
      WHERE [Incident date] = 2010) AS a, 
     (SELECT COUNT(Reference) AS totalyear2 
      FROM STO.dbo.STOMaritimeIncidents 
      WHERE [Incident date] = 2009) AS b

您可以通过在一个查询中执行此操作来改进此功能：

SELECT SUM(CASE WHEN [Incident date] = 2010 THEN 1 ELSE 0) as totalyear1,
       SUM(CASE WHEN [Incident date] = 2009 THEN 1 ELSE 0) as totalyear2
FROM STO.dbo.STOMaritimeIncidents

如果你不介意（或更喜欢）转动数据，你可以使用@Umair的建议并使用带有GROUP BY子句的COUNT。

Answer 2

P.s你可以在一个查询中完成所有事情！如

SELECT [Incident date], Total = COUNT(Reference) 
FROM STO.dbo.STOMaritimeIncidents
GROUP BY [Incident date]
WHERE [Incident date] IN (2009, 2010)

至于你的实际错误，是因为行...WHERE [Incident date] = 2009 AS totalyear2等。它需要采用以下格式（别名'需要在列上）

SELECT totalyear2 = COUNT(Reference) FROM STO.dbo.STOMaritimeIncidents WHERE [Incident date] = 2010

多个独立输出的多个SELECT语句

2 个答案: