Question

我有一个查询，该查询从两个表TABLE_1和TABLE_2中选择数据。这两个表用id连接。 TABLE_1中的每一行在TABLE_2上可以正好有4行。客户需要一个View，该View返回TABLE_1中的所有数据和TABLE_2中的所有数据，但是TABLE_2中的数据必须显示为与同一行中的列相同。例如：

这是我使用过的查询：

Select ID, NAME, LASTNAME,
(SELECT HomeType from #TABLE_2 where id = t1.ID order by ID OFFSET 0 ROW FETCH NEXT 1 ROW ONLY) as Row1Column1,
(SELECT HomeCost from #TABLE_2 where id = t1.ID order by ID OFFSET 0 ROW FETCH NEXT 1 ROW ONLY) as Row1Column2,
(SELECT HomeType from #TABLE_2 where id = t1.ID order by ID OFFSET 1 ROW FETCH NEXT 1 ROW ONLY) as Row2Column1,
(SELECT HomeCost from #TABLE_2 where id = t1.ID order by ID OFFSET 1 ROW FETCH NEXT 1 ROW ONLY) as Row2Column2,
(SELECT HomeType from #TABLE_2 where id = t1.ID order by ID OFFSET 2 ROW FETCH NEXT 1 ROW ONLY) as Row2Column1,
(SELECT HomeCost from #TABLE_2 where id = t1.ID order by ID OFFSET 2 ROW FETCH NEXT 1 ROW ONLY) as Row2Column2,
(SELECT HomeType from #TABLE_2 where id = t1.ID order by ID OFFSET 3 ROW FETCH NEXT 1 ROW ONLY) as Row2Column1,
(SELECT HomeCost from #TABLE_2 where id = t1.ID order by ID OFFSET 3 ROW FETCH NEXT 1 ROW ONLY) as Row2Column2 from #TABLE_1 as t1

我的数据示例是

CREATE TABLE #TABLE_1(ID int, NAME varchar(100), LASTNAME varchar(100))
CREATE TABLE #TABLE_2(ID int,HomeType varchar(100), HomeCost varchar(100) )



Insert into #TABLE_1 (ID, NAME, LASTNAME) VALUES (1, 'JOHN', 'SNOW')
Insert into #TABLE_2 (ID, HomeType, HomeCost) VALUES (1, 'Type1', 'Cost1')
 Insert into #TABLE_2 (ID, HomeType, HomeCost) VALUES (1, 'Type2', 'Cost2')
 Insert into #TABLE_2 (ID, HomeType, HomeCost) VALUES (1, 'Type3', 'Cost3')
 Insert into #TABLE_2 (ID, HomeType, HomeCost) VALUES (1, 'Type4', 'Cost4')

我想要这样的结果，但是对于50000行，它会变慢

ID| NAME| ROW1COLUMN1 | ROW1COLUMN2 | ROW2COLUMN1 | ROW2COLUMN2 | ROW3COLUMN1 | ROW3COLUMN2 | ROW4COLUMN1 | ROW4COLUMN2
-------------------------
 1|JOHN | Type1       | Cost1       | Type2       | Cost2       | Type3     | Cost3         | Type4       | Cost4

Answer 1

我没有测试此查询，但它应该可以工作。不要忘记为ID的HomeType字段做索引。如果字段“ HomeType”是动态的，则需要添加其他字段“ pos”。对于具有相同ID的TABLE_2中的行，“ pos”字段应唯一。

SELECT t.ID, t.NAME, t.LASTNAME, t1.HomeType AS Row1Column1, t1.HomeCost AS Row1Column2, t2.HomeType AS Row2Column1, t2.HomeCost AS Row2Column2, t3.HomeType AS Row3Column1, t3.HomeCost AS Row3Column2, t4.HomeType AS Row4Column1, t4.HomeCost AS Row4Column2
FROM TABLE_1 t
JOIN TABLE_2 t1 ON t.ID = t1.ID AND t1.HomeType = 'Type1'
JOIN TABLE_2 t2 ON t.ID = t2.ID AND t2.HomeType = 'Type2'
JOIN TABLE_2 t3 ON t.ID = t3.ID AND t3.HomeType = 'Type3'
JOIN TABLE_2 t4 ON t.ID = t4.ID AND t4.HomeType = 'Type4'

Answer 2

如果您具有相同的四种类型，则可以使用如下条件聚合：

var occupationSchema = new mongoose.Schema({
    occupationName: String
});

Answer 3

您可以使用PIVOT

WITH T2 AS (
    SELECT 
        ID, 
        HomeTypeRN = 'A' + CAST( ROW_NUMBER() OVER (PARTITION BY ID ORDER BY HomeType) AS VARCHAR),
        HomeType, 
        HomeCostRN = 'B' + CAST(ROW_NUMBER() OVER (PARTITION BY ID ORDER BY HomeType) AS VARCHAR), 
        HomeCost
    FROM #TABLE_2
)
SELECT 
    T1.ID, T1.Name, T1.LastName, [A1], [B1], [A2], [B2], [A3], [B3], [A4], [B4]
FROM #TABLE_1 T1
LEFT JOIN
(
    SELECT ID, 
    MAX(A1) AS A1, MAX(B1) AS B1, 
    MAX(A2) AS A2, MAX(B2) AS B2, 
    MAX(A3) AS A3, MAX(B3) AS B3, 
    MAX(A4) AS A4, MAX(B4) AS B4 
    FROM T2 
    PIVOT(
        MAX(HomeType) FOR HomeTypeRN IN ([A1],[A2],[A3],[A4])
    ) P1
    PIVOT(
        MAX(HomeCost) FOR HomeCostRN IN ([B1],[B2],[B3],[B4])
    ) P2
    GROUP BY ID
) P  ON P.ID = T1.ID

有没有一种方法可以提高在select子句中使用多个子查询的查询的性能

3 个答案: