我想在SQL中编写脚本,将这两个表(A,B)复制到其他2个表(C,D),结构与A,B相同。
重要:
表A具有表B的外键(fk_a_b)
________________________ _________________
| Table A | | Table B |
|______________________| |_______________|
| id FK_A_B name | | id visible |
| ----- -------- ------| | ----- --------|
| 1 21 n1 | | 21 true |
| 5 32 n2 | | 32 false |
------------------------ -----------------
假设将表B复制到D后,这就是我得到的
________________
| Table D |
|______________|
| id visible |
| ----- -------|
| 51 true |
| 52 false |
----------------
现在,当我将表A复制到C时,我需要知道,ID = 21现在映射到ID = 51,ID = 32到ID = 52。最后,表C将是:
________________________
| Table C |
|______________________|
| id FK_C_D name |
| ----- -------- ------|
| 61 51 n1 |
| 62 52 n2 |
------------------------
因为几个进程可能同时调用脚本,所以我不能改变表A,B来添加一些辅助列。所以,为了达到这个目的,我使用了CURSOR。我逐行复制了表B和托管临时表,将OldId映射到NewId(21-> 51,32-> 52),然后使用此临时表复制表A.
我读过CURSOR是不好的做法。那么,还有另一种方法吗?
谢谢
答案 0 :(得分:7)
您可以将输出子句与merge语句一起使用,以获取源标识和目标标识之间的映射。 在这个问题中描述。 Using merge..output to get mapping between source.id and target.id
以下是您可以测试的一些代码。我使用表变量而不是真实的表。
设置样本数据:
-- @A and @B is the source tables
declare @A as table
(
id int,
FK_A_B int,
name varchar(10)
)
declare @B as table
(
id int,
visible bit
)
-- Sample data in @A and @B
insert into @B values (21, 1),(32, 0)
insert into @A values (1, 21, 'n1'),(5, 32, 'n2')
-- @C and @D is the target tables with id as identity columns
declare @C as table
(
id int identity,
FK_C_D int not null,
name varchar(10)
)
declare @D as table
(
id int identity,
visible bit
)
-- Sample data already in @C and @D
insert into @D values (1),(0)
insert into @C values (1, 'x1'),(1, 'x2'),(2, 'x3')
复制数据:
-- The @IdMap is a table that holds the mapping between
-- the @B.id and @D.id (@D.id is an identity column)
declare @IdMap table(TargetID int, SourceID int)
-- Merge from @B to @D.
merge @D as D -- Target table
using @B as B -- Source table
on 0=1 -- 0=1 means that there are no matches for merge
when not matched then
insert (visible) values(visible) -- Insert to @D
output inserted.id, B.id into @IdMap; -- Capture the newly created inserted.id and
-- map that to the source (@B.id)
-- Add rows to @C from @A with a join to
-- @IdMap to get the new id for the FK relation
insert into @C(FK_C_D, name)
select I.TargetID, A.name
from @A as A
inner join @IdMap as I
on A.FK_A_B = I.SourceID
结果:
select *
from @D as D
inner join @C as C
on D.id = C.FK_C_D
id visible id FK_C_D name
----------- ------- ----------- ----------- ----------
1 1 1 1 x1
1 1 2 1 x2
2 0 3 2 x3
3 1 4 3 n1
4 0 5 4 n2
您可以在此处测试代码:http://data.stackexchange.com/stackoverflow/q/101643/using-merge-to-map-source-id-to-target-id
答案 1 :(得分:0)
E.g。 SQL Server将rowguid字段添加到某些发布中包含的用于合并复制的表中。我认为,这种方法可以用在你的任务中。我们的想法是添加几个将扮演pf全局标识符角色的GUID字段,因此我们可以在两个master-datails表对中使用它们
答案 2 :(得分:0)
您可以这样做:
if object_id('tempdb..#TableB') is not null
drop table #TableB
select identity(int) RowId, *
into #TableB
from TableB
if object_id('tempdb..#TableDIds') is not null
drop table #TableDIds
create table #TableDIds (RowId int identity(1,1), Id int)
insert TableD
output inserted.Id into #TableDIds
select Visible
from #TableB
order by RowId
insert TableC
select tdi.Id, ta.name
from TableA ta
join #TableB tb on
ta.FK_A_B = tb.Id
join #TableDIds tdi on
tdi.RowId = tb.RowId
我使用了以下设置:
create table TableB
(
Id int not null primary key,
Visible bit not null
)
create table TableA
(
Id int not null,
FK_A_B int not null foreign key references TableB(Id),
Name varchar(10) not null
)
create table TableD
(
Id int identity(1,1) primary key,
Visible bit not null
)
create table TableC
(
Id int identity(1,1),
FK_C_D int not null references TableD(Id),
Name varchar(10) not null
)
insert TableB
values
(21, 1),
(32, 0)
insert TableA
values
(1, 21, 'n1'),
(5, 32, 'n2')
答案 3 :(得分:0)