动态SQL语句根据数据库列来查询数据，动态的生成列名称

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

/******************************************************************************************
----------------------------------------------------------------------------------------
存储过程名称：  [contract_station_elec]
实现功能：    基准站月用电量统计报表
作者：      巫航

----------------------------------------------------------------------------------------
修改时间    版本号    修改人  修改摘要
2013年4月26日    V3.0    巫航    创建该存储过程，由于辽宁电信的需求，需要按各用电量电流值current_size来分割大小
----------------------------------------------------------------------------------------
******************************************************************************************/
alter PROCEDURE [dbo].[rpt_contract_station_elec]
@station varchar(8000) = '',
@time    varchar(8000) = '',
@time_start datetime = null,
@time_end   datetime = null,
@sort       varchar(8000) = ''
as
begin
set nocount on;

declare @nv_table_name nvarchar(max); --表名称变量
declare @nv_sql nvarchar(max);        --动态sql变量
declare @v_station_kind int;
declare @v_name varchar(30);
declare @nv_column_name nvarchar(max);--SUM+列名称
DECLARE @table VARCHAR(8000)
DECLARE @sql nvarchar(max);

SET @table = 'his_powermonth_' +
CONVERT(VARCHAR(8000), DATEPART(yy, @time_start))
--如果表不存在，使用没有数据的原始表
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[' + @table + ']') AND type in (N'U'))
BEGIN
set @table = 'his_powermonth'
END
--创建临时表,放置局站
DECLARE @station_where VARCHAR(8000)
SET @station_where = ''
IF @station<>''
BEGIN
IF object_id('tempdb..#TEMPTB1') is not null
drop table #TEMPTB1
CREATE table #TEMPTB1
(
station_sn VARCHAR(64)
)
CREATE clustered index #TEMPTB1_Index1 on #TEMPTB1 (station_sn)
SET @sql = 'INSERT INTO #TEMPTB1 ' + @station
EXEC(@sql)
SET @station_where = 'INNER JOIN #TEMPTB1 tmp ON t.station_sn = tmp.station_sn'
END

--删除可能存在的临时表
if object_id('tempdb..#temp_a') is not null
begin
drop table #temp_a;
end
--建立遥测量临时表
CREATE TABLE #temp_a(
[station_sn] varchar(64) not null,
[current_size] tinyint,
[value] real
);
SET @sql = 'INSERT INTO #temp_a([station_sn],[current_size],[value])
select t.[station_sn],t.[current_size],sum(t.[value]) as [value]
FROM '+@table+' t ' + @station_where +' group by t.[current_size],t.[station_sn]'

exec(@sql);
--    select * from #temp_a;
--    insert into #temp_a([station_sn],[am_kind],[value]) SELECT [station_sn],[am_kind],sum([value]) as [value] FROM [ems_his].[dbo].[his_powermonth_2013]
--group by [am_kind],station_sn

--删除可能存在的临时表
if object_id('tempdb..#temp_table') is not null
begin
drop table #temp_table;
end
--建立电流值大小临时表
CREATE TABLE #temp_table(
[current_size] int not null
);

set @nv_table_name = ' a.*';
set @nv_column_name = '';

declare cs1 cursor for
select [name] from [ems_cfg].[dbo].[cfg_currentsize]
open cs1
fetch next from cs1 into @v_name
while @@fetch_status = 0
begin
set @nv_table_name = @nv_table_name + ' ,b.[' +@v_name+']*a.value as ['+@v_name +']';
set @nv_column_name = @nv_column_name + ' ,ROUND(SUM(['+@v_name+']),2) as ['+@v_name+']'
select @nv_sql = 'alter table #temp_table add [' + @v_name + '] int default 0';
--print(@nv_sql);
exec(@nv_sql);
fetch next from cs1 into @v_name;
end
close cs1
deallocate cs1

insert into #temp_table(current_size)
select current_size from [ems_cfg].[dbo].[cfg_currentsize]

declare cs2 cursor for
select [current_size],[name] from [ems_cfg].[dbo].[cfg_currentsize]
open cs2
fetch next from cs2 into @v_station_kind,@v_name
while @@fetch_status = 0
begin
select @nv_sql = 'update #temp_table set [' + @v_name + '] = 1
where [current_size] = ' + rtrim(@v_station_kind);
print(@nv_sql);
exec(@nv_sql);
fetch next from cs2 into @v_station_kind,@v_name;
end
close cs2
deallocate cs2

--  select [am_kind] from [ems_cfg].[dbo].[cfg_amkind];
--  select * from #temp_table;

set @nv_table_name ='select s.station_name,l.lsc_name,p.precinct_name,'+ @nv_table_name +
' from #temp_a a
left join #temp_table b on a.[current_size] = b.[current_size]
left join ems_cfg.dbo.cfg_station s on s.station_sn=a.station_sn
left join ems_cfg.dbo.cfg_lsc l on l.lsc_id=s.lsc_id
left join ems_cfg.dbo.cfg_precinct p on p.lsc_id=l.lsc_id and p.precinct_id=s.precinct_id';
set @nv_sql = 'select station_name,lsc_name,precinct_name'+@nv_column_name+' from ('+@nv_table_name+') t
group by station_name,lsc_name,precinct_name'
print(@nv_sql);
exec(@nv_sql);

--查询出第二个表
SELECT [current_size],[name] FROM [ems_cfg].[dbo].[cfg_currentsize]
end