Question

我是SQL的新手，我正在编写此查询

SELECT
    SalesreturnDetails.[Price]
FROM
    SalesreturnDetails,
    SalesReturn
WHERE
    SalesReturn.Session='12-13';

但在SalesReturn表中有两个记录，而SalesreturnDetails表有3个记录，但输出有6行，但我想输出应该是3行。

表格是： SalesReturn

Bill_Number    Session
 2              12-13
 2              12-13

SalesReturnDetails

Bill_Number    Price
  2             700
  2             900
  2             300

Answer 1

您应该在Bill_Number上尝试外部联接：http://en.wikipedia.org/wiki/Join_(SQL)

Answer 2

SELECT  a.Price
FROM    SalesReturnDetails a
        INNER JOIN 
        (
            SELECT  DISTINCT Bill_number
            FROM    SalesReturn
            WHERE   Session='12-13'
        ) b ON a.Bill_number = b.Bill_number

SQLFiddle Demo

从两个表中获取单列

2 个答案: