删除重复的行集

Question

数据

CREATE TABLE #tbl_LinkedInvoices(
    InvoiceNbr              varchar(50)
,   AssociatedInvoiceNbr    varchar(50)
,   RowNbr                  int
,   AssociatedRowNbr        int
)
INSERT INTO #tbl_LinkedInvoices(
        InvoiceNbr, AssociatedInvoiceNbr, RowNbr, AssociatedRowNbr)
VALUES 
    ('A0001', 'A1001', 1, 4),
    ('A0002', 'A2002', 2, 5),
    ('A0002', 'A3002', 3, 6),
    ('A1001', 'A0001', 4, 1),
    ('A2002', 'A0002', 5, 2),
    ('A3002', 'A0002', 6, 3)

    SELECT * FROM #tbl_LinkedInvoices

挑战/目标

tbl_LinkedInvoices 用于识别链接到的AssociatedInvoiceNbrs b 和InvoiceNbr a。因此，从(a, b) = (b,a) 起，一个集合可以在表中出现多次。为了解决这些重复出现的问题，添加了 RowNbr 和 AssociatedRowNbr 字段以提供分组序列。

使用已识别的重复行，删除重复行，在表中保留一条唯一记录。当前脚本产生错误，期待可能有更好的方法来编写查询。

脚本

使用计数器检查重复行是否仍然存在，如果确实删除该行，直到FALSE。

DECLARE @RowCounter int
DECLARE @RemoveRow int
SET @RowCounter = 1



IF EXISTS (SELECT 
              RowNbr
           FROM #tbl_LinkedInvoices WHERE RowNbr = (SELECT AssociatedRowNbr FROM #tbl_LinkedInvoices)
)
BEGIN
   SET @RemoveRow = (SELECT RowNbr FROM #tbl_LinkedINvoices
                     WHERE RowNbr = (
                            SELECT AssociatedRowNbr FROM #tbl_LinkedInvoices WHERE RowNbr =@RowCounter ))
    BEGIN
        DELETE FROM #tbl_LinkedInvoices
        WHERE
        RowNbr = @RemoveRow
    END
    BEGIN
        SET @RowCounter = @RowCounter + 1
    END
END

错误

Msg 512, Level 16, State 1, Line 212
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

Answer 1

如果我正确地跟着你，你可以在单个语句中执行“镜像”记录的删除，而无需使用额外的计算列：

delete t
from #tbl_LinkedInvoices t
where exists (
    select 1 
    from #tbl_LinkedInvoices t1 
    where 
        t1.AssociatedInvoiceNbr = t.InvoiceNbr
        and t1.InvoiceNbr = t.AssociatedInvoiceNbr
        and t1.AssociatedInvoiceNbr > t.AssociatedInvoiceNbr
)

这会删除镜像记录，同时保留InvoiceNbr 小于AssociatedInvoiceNbr 的记录。

Demo on DB Fiddle 与您的示例数据。

delete语句执行后，表的内容为：

发票Nbr | AssociatedInvoiceNbr |行号 |关联行号 :--------- | :-------------------- | -----: | ---------------： A0001 | A1001 | 1 | 4 A0002 | A2002 | 2 | 5 A0002 | A3002 | 3 | 6