sql - SQL Server 2008 列出不在表中的项目

Question

一个简单的查询，应该查看systemSoftware表格和软件表格，并只显示softwareId不在systemSoftware表格内的内容。

到目前为止，这是我的查询...

SELECT s.softwareId AS 'Software ID',
    s.softwareDescription AS 'Software Description',
    sv.vendorName AS 'Vendor Name',
    c.cityName AS 'City Name'
FROM software AS s
JOIN systemSoftware AS ss
ON s.softwareId = ss.softwareId
JOIN softwareVendor AS sv
ON s.vendorId = sv.vendorId
JOIN city AS c
ON sv.zipCode = c.zipCode
WHERE s.softwareId NOT IN (ss.softwareId)
ORDER BY s.softwareId
GO

当我删除 NOT 时，它会softwareId显示systemSoftware.

问题是我想要相反的。那些不在systemSoftware.

Answer 1

你需要一个左外连接：

SELECT ss.softwareId AS 'Software ID',
    s.softwareDescription AS 'Software Description',
    sv.vendorName AS 'Vendor Name',
    c.cityName AS 'City Name'
FROM software AS s
left outer JOIN systemSoftware AS ss
ON s.softwareId = ss.softwareId
left outer JOIN softwareVendor AS sv
ON s.vendorId = sv.vendorId
left outer JOIN city AS c
ON sv.zipCode = c.zipCode
WHERE ss.softwareId is NULL
ORDER BY s.softwareId

我还更改了ORDER BY, 因为按不存在的列排序是没有意义的。