使用SQL查找不匹配的记录

Question

我正在尝试编写查询来查找在另一个表中没有匹配记录的记录.

例如,我有两个表,其结构如下所示:

Table1
    State | Product | Distributor | other fields
    CA    | P1      |  A          | xxxx
    OR    | P1      |  A          | xxxx
    OR    | P1      |  B          | xxxx
    OR    | P1      |  X          | xxxx
    WA    | P1      |  X          | xxxx
    VA    | P2      |  A          | xxxx

Table2
    State | Product | Version | other fields
    CA    | P1      |  1.0    | xxxx
    OR    | P1      |  1.5    | xxxx
    WA    | P1      |  1.0    | xxxx
    VA    | P2      |  1.2    | xxxx

(州/产品/分销商共同构成表1的关键.州/产品是表2的关键)

我想找到所有未使用经销商X的州/产品/版本组合.(因此本例中的结果是CA-P1-1.0和VA-P2-1.2.)

有关查询的任何建议吗？

Answer 1

SELECT
    *
FROM
    Table2 T2
WHERE
    NOT EXISTS (SELECT *
        FROM
           Table1 T1
        WHERE
           T1.State = T2.State AND
           T1.Product = T2.Product AND
           T1.Distributor = 'X')

这应该符合ANSI标准.

Answer 2

在T-SQL中:

SELECT DISTINCT Table2.State, Table2.Product, Table2.Version
FROM Table2 
  LEFT JOIN Table1 ON Table1.State = Table2.State AND Table1.Product = Table2.Product AND Table1.Distributor = 'X'
WHERE Table1.Distributor IS NULL

不需要子查询.

编辑:正如评论所示,DISTINCT不是必需的.谢谢!