假设我有以下简单的表变量:
declare @databases table
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into @databases
如果我想遍历各行,声明和使用游标是我唯一的选择吗?还有别的办法吗?
假设我有以下简单的表变量:
declare @databases table
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into @databases
如果我想遍历各行,声明和使用游标是我唯一的选择吗?还有别的办法吗?
当前回答
SELECT @pk = @pk + 1
会更好:
SET @pk += @pk
避免使用SELECT如果你没有引用表,只是分配值。
其他回答
这是我使用的2008 R2代码。我使用的这段代码是在所有故事的关键字段(SSNO & EMPR_NO)上构建索引
if object_ID('tempdb..#a')is not NULL drop table #a
select 'IF EXISTS (SELECT name FROM sysindexes WHERE name ='+CHAR(39)+''+'IDX_'+COLUMN_NAME+'_'+SUBSTRING(table_name,5,len(table_name)-3)+char(39)+')'
+' begin DROP INDEX [IDX_'+COLUMN_NAME+'_'+SUBSTRING(table_name,5,len(table_name)-3)+'] ON '+table_schema+'.'+table_name+' END Create index IDX_'+COLUMN_NAME+'_'+SUBSTRING(table_name,5,len(table_name)-3)+ ' on '+ table_schema+'.'+table_name+' ('+COLUMN_NAME+') ' 'Field'
,ROW_NUMBER() over (order by table_NAMe) as 'ROWNMBR'
into #a
from INFORMATION_SCHEMA.COLUMNS
where (COLUMN_NAME like '%_SSNO_%' or COLUMN_NAME like'%_EMPR_NO_')
and TABLE_SCHEMA='dbo'
declare @loopcntr int
declare @ROW int
declare @String nvarchar(1000)
set @loopcntr=(select count(*) from #a)
set @ROW=1
while (@ROW <= @loopcntr)
begin
select top 1 @String=a.Field
from #A a
where a.ROWNMBR = @ROW
execute sp_executesql @String
set @ROW = @ROW + 1
end
可以使用游标来做到这一点:
创建函数[dbo].f_teste_loop 返回@tabela表 ( 鳕鱼int, 省varchar (10) ) 作为 开始
insert into @tabela values (1, 'verde');
insert into @tabela values (2, 'amarelo');
insert into @tabela values (3, 'azul');
insert into @tabela values (4, 'branco');
return;
end
创建过程[dbo].[sp_test_loop] 作为 开始
DECLARE @cod int, @nome varchar(10);
DECLARE curLoop CURSOR STATIC LOCAL
FOR
SELECT
cod
,nome
FROM
dbo.f_teste_loop();
OPEN curLoop;
FETCH NEXT FROM curLoop
INTO @cod, @nome;
WHILE (@@FETCH_STATUS = 0)
BEGIN
PRINT @nome;
FETCH NEXT FROM curLoop
INTO @cod, @nome;
END
CLOSE curLoop;
DEALLOCATE curLoop;
end
这将在SQL SERVER 2012版本中工作。
declare @Rowcount int
select @Rowcount=count(*) from AddressTable;
while( @Rowcount>0)
begin
select @Rowcount=@Rowcount-1;
SELECT * FROM AddressTable order by AddressId desc OFFSET @Rowcount ROWS FETCH NEXT 1 ROWS ONLY;
end
我是这样做的:
declare @RowNum int, @CustId nchar(5), @Name1 nchar(25)
select @CustId=MAX(USERID) FROM UserIDs --start with the highest ID
Select @RowNum = Count(*) From UserIDs --get total number of records
WHILE @RowNum > 0 --loop until no more records
BEGIN
select @Name1 = username1 from UserIDs where USERID= @CustID --get other info from that row
print cast(@RowNum as char(12)) + ' ' + @CustId + ' ' + @Name1 --do whatever
select top 1 @CustId=USERID from UserIDs where USERID < @CustID order by USERID desc--get the next one
set @RowNum = @RowNum - 1 --decrease count
END
没有游标,没有临时表,没有额外的列。 USERID列必须是唯一的整数,就像大多数主键一样。
如果您别无选择,只能逐行创建FAST_FORWARD游标。它和构建while循环一样快,而且更容易长期维护。
FAST_FORWARD 指定一个启用性能优化的FORWARD_ONLY、READ_ONLY游标。如果还指定了SCROLL或FOR_UPDATE,则FAST_FORWARD不能指定。