带有多个where子句的SQL查询

Question

我试图在SSRS中为数据集编写查询。我有一个名为RequestSchools的连接表，它连接到另外三个表：

1. 学校
2. 提出请求
3. RequestSchoolType

我想获得RequestedSchool (RequestedSchoolTypeId = 3)

的名称

我还想要CatchmentSchool (RequestSchoolTypeId = 1)

的名称

我附上了我可以与所请求的学校合作的SQL查询图片。我也想要集水学校。感谢任何帮助。

SELECT
    pr.PlacingRequestId, s.Name AS RequestedSchool
FROM  
    PlacingRequests AS pr 
INNER JOIN 
    RequestSchools AS rs ON rs.PlacingRequestId = pr.PlacingRequestId 
JOIN
    Schools s ON s.SchoolId = rs.SchoolId
WHERE
    rs.RequestSchoolTypeId = 3

Answer 1

我不是100％确定这是正确的，因为我们无法看到架构，源数据或所需输出的完整示例，但我认为这可能是它：

SELECT 
  pr.PlacingRequestId, 
  s.Name as RequestedSchool,
  cs.Name as CatchmentSchool
FROM 
  PlacingRequests AS pr 
  INNER JOIN RequestSchools AS rs 
    ON rs.PlacingRequestId = pr.PlacingRequestId 
  INNER JOIN Schools s 
    on s.SchoolId = rs.SchoolId
    AND rs.RequestSchoolTypeId = 3 -- requested school
  INNER JOIN Schools cs 
    on cs.SchoolId = rs.SchoolId
    AND rs.RequestSchoolTypeId = 1 -- catchment school

如果不是您的意思，请尽快更新，并且您可以按照指示澄清问题。

Answer 2

根据我对您的要求的理解，您将需要多个连接而不是where子句中的另一个AND条件。因此，我们可以省略这里的位置，并再次将学校与学校一起加入CatchmentSchool，因为我们已经为Requestedschool做过一次。唯一的区别是我们在加入时使用requestedtypeid和catchmenttypeid值。

Select 
pr.PlacingRequestId, 
rs.Name as RequestedSchool
cs.Name as CatchmentSchool
FROM 
PlacingRequests AS pr 
INNER JOIN RequestSchools AS rrs 
ON rrs.PlacingRequestId = pr.PlacingRequestId 
and rrs.RequestSchoolTypeId = 3 
JOIN Schools rs 
on rs.SchoolId = rrs.SchoolId
INNER JOIN RequestSchools AS crs 
ON crs.PlacingRequestId = pr.PlacingRequestId 
and crs.RequestSchoolTypeId = 1 
JOIN Schools cs 
on cs.SchoolId = crs.SchoolId

希望这会有所帮助......

Answer 3

执行此操作的最佳方法是使用CASE函数，但我不知道您使用的是哪个RDBMS，因此这里是强力方法：只需将查询作为两个子查询运行，每个子查询指定不同的类型ID然后加入他们。它会是这样的：

SELECT DISTINCT catch.placingrequestid, catch.catchmentschool, requested.requestedschool
FROM
(SELECT pr.placingrequestid, s.nam as catchmentschool
FROM (PlacingRequest pr
INNER JOIN RequestSchools rs ON pr.placingrequestid = rs.placingrequestid)
INNER JOIN School s ON rs.schoolid = s.schoolid
WHERE rs.requestschooltypeid = 1) catch
INNER JOIN
(SELECT pr.placingrequestid, s.nam as requestedschool
FROM (PlacingRequest pr
INNER JOIN RequestSchools rs ON pr.placingrequestid = rs.placingrequestid)
INNER JOIN School s ON rs.schoolid = s.schoolid
WHERE rs.requestschooltypeid = 3) requested
ON catch.placingrequestid = requested.placingrequestid