我有下表:
ID TableName FieldName
1 tbl1 fieldA
1 tbl1 fieldB
2 tbl2 fieldC
2 tbl2 fieldD
ddl在
之下Declare @tblPlaceholder table(ID int,TableName Nvarchar(20),FieldName Nvarchar(20))
insert into @tblPlaceholder
select 1,'tbl1','fieldA' union all select 1,'tbl1','fieldB' union all
select 2,'tbl2','fieldC' union all select 2,'tbl2','fieldD'
select * from @tblPlaceholder
我需要做的是,在运行时我需要使用字段和表名来构造查询,从此我需要执行它们。
因此,在运行时,要形成的查询是
ID Query
1 Select tbl1.fieldA,tbl1.fieldB from tbl1
2 Select tbl2.fieldC,tbl2.fieldD from tbl2
我的查询不足,效果很好
-- Step 1: Build the query and insert the same into a table variable
Insert into @t
Select ID, Query = ' Select ' + FieldNames + ' from ' + TableName
From
(
Select ID,TableName, FieldNames = Stuff((select ',' + CAST(TableName as Nvarchar(20)) + '.' + CAST(FieldName as Nvarchar(20))
from @tblPlaceholder t2 where t2.ID = t1.ID
FOR XML PATH('')),1,1,'')
From @tblPlaceholder t1
Group By t1.ID,t1.TableName)X
/* output of step 1
select * from @t
ID Query
1 Select tbl1.fieldA,tbl1.fieldB from tbl1
2 Select tbl2.fieldC,tbl2.fieldD from tbl2
*/
-- Step 2 : loop thru the ID and execute the queries
While (@i <= 2) -- since there are two id's.. this can even be configurable as max(id)
Begin
SELECT @QueryList = (Select Query from @t where ID = @i)
exec(@QueryList)
set @i += 1
End
但我很确定即使以更好的方式也可以做到。我一直在寻找 sp_MSforeachtable ,但我不确定我们是否可以这样做?
请问有人请帮助我。
答案 0 :(得分:0)
我做了一个例子。调整它以符合您的需求。
DECLARE @mytable AS VARCHAR(100)
DECLARE @sql AS VARCHAR(1000)
DECLARE mycursor CURSOR FOR
SELECT name
FROM sys.tables
-- WHERE your conditions here!
OPEN mycursor
FETCH NEXT FROM mycursor INTO @mytable
WHILE @@FETCH_STATUS = 0
BEGIN
SET @sql = 'SELECT * FROM ' + @tablename -- Define the query string. replace with your code
EXEC(@sql) -- execure the query
FETCH NEXT FROM mycursor INTO @mytable
END
CLOSE mycursor
DEALLOCATE mycursor