Question

我在SQL Server 2005中有一个表，如下所示

DECLARE @Promotions TABLE (PromoCode VARCHAR(10),
                          DeptID VARCHAR(10),
                          VerticalID VARCHAR(10),
                          BuildingID VARCHAR(10)
                          primary key (DeptID, VerticalID, BuildingID)
                        )

INSERT INTO @Promotions VALUES ('P1_20%','101','501','1001')
INSERT INTO @Promotions VALUES ('P2_10%','101','501','All')
INSERT INTO @Promotions VALUES ('P3_5%','101','All','All')
INSERT INTO @Promotions VALUES ('P1_50%','111','606','1002')

我们需要根据DeptID，VerticalID和BuildingID列中的匹配值找出促销代码值。如果与这3列不匹配，请查找与DeptID，VerticalID的输入值和BuildingID的默认值（“全部”）匹配的匹配项。如果找不到结果，请考虑输入DeptID，VerticalID的默认值（“全部”）和BuildingID的默认值（“全部”）来查找匹配项。< / p>

以下查询工作正常 - 但它使用的是3部分方法。我们可以在单个SQL查询中实现这一点吗？

现有代码

DECLARE @PromoCode VARCHAR(10)

--Part 1
SELECT @PromoCode = PromoCode
FROM @Promotions
WHERE DeptID = @inputDeptID
  AND VerticalID = @inputVerticalID
  AND BuildingID = @inputBuildingID

--Part 2
IF @PromoCode IS NULL 
BEGIN
    SELECT @PromoCode = PromoCode
    FROM @Promotions
    WHERE DeptID = @inputDeptID
      AND VerticalID = @inputVerticalID
      AND BuildingID = 'All'
END

--Part 3
IF @PromoCode IS NULL 
BEGIN
    SELECT @PromoCode = PromoCode
    FROM @Promotions
    WHERE DeptID = @inputDeptID
      AND VerticalID = 'All'
      AND BuildingID = 'All'
END

--Result
SELECT @PromoCode

测试

DECLARE @inputDeptID VARCHAR(10)
DECLARE @inputVerticalID VARCHAR(10)
DECLARE @inputBuildingID VARCHAR(10)

SET @inputDeptID = '101'
SET @inputVerticalID = '501'
SET @inputBuildingID = '3003'

预期结果

P2_10%

Answer 1

您可以将其视为“优先级”。也就是说，查找所有可能的匹配项，然后使用order by和top选择最合适的匹配项：

set @PromoCode = (SELECT top 1 PromoCode
                  FROM @Promotions
                  WHERE DeptID = @inputDeptID AND
                        (VerticalID = @inputVerticalID OR VerticalId = 'ALL') AND
                        (BuildingID = @inputBuildingID OR BuildingID = 'ALL')
                  ORDER BY (case when Building = 'ALL' then 1 else 0 end),
                           (case when VerticalId = 'ALL' then 1 else 0 end)
                 );

还有其他方法可以表达这一点。如果性能存在问题并且列上有索引，那么使用union all order by方法可能比or子句中的where更好。

将多个SQL组合成一个Query

1 个答案: