加法更新插入

Question

在 Microsoft SQL Server 2008 中您将如何编写以下内容？

IF EXISTS(SELECT * FROM Table WHERE Something=1000)
UPDATE Table SET Qty = Qty + 1 WHERE Something=1000
ELSE
INSERT INTO Table(Something,Qty) VALUES(1000,1)

Answer 1

IF EXISTS(SELECT * FROM Table WHERE Something=1000)
BEGIN
 UPDATE Table SET Qty = Qty + 1 WHERE Something=1000
END
ELSE
BEGIN
 INSERT INTO Table(Something,Qty) VALUES(1000,1)
END

Answer 2

据我所知，使用 SQL Server 2008 中新的 merge 命令会发现：

merge Table t
using (select 1000 as Something, 1 as Qty) s on t.Something = s.Something
when matched then
  update set t.Qty = t.Qty + 1
when not matched by target then
  insert values (s.Something, s.Qty);

这并不那么简单，因为合并对于合并更大的集合（而不仅仅是单个记录）来说更有效。否则，您可以尝试更新记录，如果没有更新记录，则插入一条记录：

update Table set Qty = Qty + 1 where Something = 1000
if (@@rowcount = 0) begin
  insert into Table (Something, Qty) values (1000, 1)
end