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T-SQL连接受限

limit join tsql sql-server

Adrian Godong · 技术社区 · 17 年前

ID (PK), Value1

BatchID, Table1ID (FK to Table 1 ID), Value2

表1:

ID  Value1
1   A
2   B

表2:

BatchID  Table1ID  Value2
1        1         100
2        1         101
3        1         102
1        2         200
2        2         201

现在,对于表1中的每条记录,我想在表2中做一个匹配记录,但只匹配最近的一条(批ID是连续的)。上述示例的结果为:

Table1.ID  Table1.Value1  Table2.Value2
1          A              102
2          B              201

LIMITing an SQL JOIN

4 回复 | 直到 9 年前

Cade Roux 17 年前

WITH Latest AS (
    SELECT Table1ID
        ,MAX(BatchID) AS BatchID
    FROM Table2
    GROUP BY Table1ID
)
SELECT *
FROM Table1
INNER JOIN Latest
    ON Latest.Table1ID = Table1.ID
INNER JOIN Table2
    ON Table2.BatchID = Latest.BatchID

Quassnoi 17 年前

SELECT  id, value1, value2
FROM    (
        SELECT  t1.id, t2.value1, t2.value2, ROW_NUMBER() OVER (PARTITION BY t1.id ORDER BY t2.BatchID DESC) AS rn
        FROM    table1 t1
        JOIN    table2 t2
        ON      t2.table1id = t1.id
        ) q
WHERE   rn = 1

SQLMenace 17 年前

select t1.*,t2.Value2
from(
select Table1ID,max(Value2) as Value2
from [Table 2]
group by Table1ID) t2
join [Table 1] t1 on t2.Table1ID = t1.id

-1

instanceof me 17 年前

SELECT * FROM Table1 a
INNER JOIN Table2 b ON (a.id = b.Table1ID)
WHERE NOT EXISTS(
      SELECT 1 FROM Table2 c WHERE c.Table1ID = a.id AND c.BatchID > b. BatchID
)

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