如何使用其他記錄更新sql中的記錄作爲值？

Question

MS SQL Server 2008 - 我有一個數據庫表，其中我有一小部分行具有近似匹配，保存爲2列，在表中的其他地方。你將如何構造SQL更新循環來遍歷子集（record1）並搜索其匹配對象（record2），然後從列（record2.columnX）複製一個值來更新其他（record1.columnX）？

前：

TxID|RecordID|ColumnA|ColumnX|ColumnY  
1 |111.222 |ggg |1234 |subset1 
2 |111.222 |ggg |3456 |subset2 
3 |111.333 |hhh |6789 |subset1 
4 |111.333 |hhh |7890 |subset2 
5 |111.444 |jjj |2345 |subset1 
5 |111.444 |jjj |5678 |subset2 

後：

TxID|RecordID|ColumnA|ColumnX|ColumnY  
1 |111.222 |ggg |1234 |subset1 
2 |111.222 |ggg |1234 |subset2 
3 |111.333 |hhh |6789 |subset1 
4 |111.333 |hhh |6789 |subset2 
5 |111.444 |jjj |2345 |subset1 
5 |111.444 |jjj |2345 |subset2 

自學成才的，比較新的SQL。耐心感謝。

Answer 1

上分（TxID添加）組內加入recordId所

update my_table t1 
    inner join 
    (
     select RecordID, ColumnA, ColumnX, ColumnY 
     from my_table 
     where (TxID, RecordID) in (
     select min(TxID), RecordID 
     from my_table 
     group by RecordID) 
) ttt on ttt.RecordID = t1.RecordID 
    set t1.ColumnX = ttt.ColumnX 

Answer 2

我會做這樣的事情你可以使用一個更新：

UPDATE table t1 SET columnX=sq.columnXmin 
FROM (
    SELECT t2.RecordID, MIN(t2.columnX) as columnXmin 
    FROM table t2 
    GROUP BY t2.RecordID 
    ) AS sq 
WHERE t1.RecordID = sq.RecordID; 

Answer 3

另一種方式來做到這一點：

UPDATE t1 
SET  t1.ColumnX = t2.ColumnX 
FROM @table t1 
     INNER JOIN @table t2 ON t1.RecordID = t2.RecordID 
           AND t1.ColumnA = t2.ColumnA 
           AND t1.ColumnY <> t2.ColumnY 
           AND t1.TxID > t2.TxID -- the lowest TxID keeps its original value 

或...

UPDATE t1 
SET  t1.ColumnX = t2.ColumnX 
FROM @table t1 
     INNER JOIN @table t2 ON t1.RecordID = t2.RecordID 
           AND t1.ColumnA = t2.ColumnA 
           AND t1.ColumnY <> t2.ColumnY 
           AND t1.TxID < t2.TxID -- the largest TxId keeps its original value