Sql Query with inner select [duplicate]

问题

This question already has answers here:

Sql query to create a calculated field (2 answers)

Closed 5 years ago.

I have this sql query:

SELECT DISTINCT
  [Card NO], 
  [User Name],  
  (
    SELECT
      MIN(DateTime) AS [Enter Time], 
      MAX(DateTime) AS [Exit Time], 
      MAX(DateTime) - MIN(DateTime) AS [Inside Hours] 
    FROM
      ExcelData
  ) 
FROM
  ExcelData
GROUP BY
  [Card NO], [User Name], DateTime

Table Schema: CardNO | UserName | DateTime

I tried to execute it but with no success. I says that it is an invalid query. Can anyone find what is wrong in this query?

回答1:

This would not resolve your possible Problems with reserved keywords and column names, but should be a valid query. You were using a select query as column Name.

SELECT
    [Card NO], 
    [User Name], 
    MIN(DateTime) AS [Enter Time], 
    MAX(DateTime) AS [Exit Time], 
    MAX(DateTime) - MIN(DateTime) AS [Inside Hours] 
  FROM
    ExcelData
  GROUP BY
     [Card NO], [User Name]

回答2:

You are grouping by DateTime, which is a reserved keyword, and you don't select a column DateTime. You do select aggregates over DateTime, which means you shouldn't group on it. @irene got the right answer.

来源：https://stackoverflow.com/questions/25929155/sql-query-with-inner-select