SQLSREVER如何创建和使用动态游标

▲创建游标

CREATE PROCEDURE Usp_CreateCursor(@Select_Command varchar(8000),@Cursor_Return CURSOR VARYING OUTPUT) AS
/*存储过程名称：Usp_CreateCursor
  功能描述：    根据指定的SELECT创建一个动态游标
  参数描述：    @Select_Command ---SELECT语句;@Cursor_Return ---要返回的游标变量
  思路：        动态游标的关键是不知如何去构造它的SELECT语句，因为SELECT是个字符串表量，定义时不能直接用它，但它可以来源于表。
                所以我的目的就是创建一个统一的表，从中取数据不就可以了。建表有一定的语法规则，所以就应该根据栏位列表生成相应的
                格式，这个可以从系统表中获取。关键的问题是如何将数据插入到临时表，我摸索出一条语句可
                实现这个功能，那就是INSERT INTO <TABLE_NAME> EXECUTE <SQL>，而SQL7.0的帮助未讲。有表有数据就可以创建了。
  创建人：      康剑民
  创建日期：    2001-07-11
*/
Declare @Select_Command_Temp Varchar(8000), ---存放SELECT临时语法
        @Table_List varchar(255), ---存放表的列表
        @Column_List varchar(8000),---存放栏位列表
        @Table_Name varchar(30),---存放单独表名
        @Column_Name varchar(30),---存放单独栏位名（但有可能是*）
        @Column_Syntax varchar(8000),---存放栏位建表时的语法（综合）
        @Column_Name_Temp varchar(30),---存放栏位名称
        @Column_Type_Temp varchar(30),----存放栏位类型
        @Column_Syntax_Temp varchar(8000),---存放栏位建表时的语法（单个）
        @Column_Length_Temp int,---存放栏位长度
        @Column_Xprec_Temp int,---存放栏位精度
        @Column_Xscale_Temp int,---存放栏位小数位数
        @From_Pos int,---存放from的位置
        @Where_Pos int,---存放where的位置
        @Having_Pos int,---存放having的位置
        @Groupby_Pos int,---存放groupby的位置
        @Orderby_Pos int,---存放orderby的位置
        @Temp_Pos int,---临时变量
        @Column_Count int,---存放栏位总数
        @Loop_Seq int---循环步进变量

---创建临时表
Create Table #Test(a int)
---如果传来的SELECT语句不是以'select'开头，自动修改
If Left(Lower(Ltrim(@Select_Command)),6) <> 'select' Select @Select_Command = 'Select ' + @Select_Command
---将开头‘SELECT’去掉
Select @Select_Command_Temp = Lower(Ltrim(@Select_Command))
If Left(@Select_Command_Temp,6) = 'select' Select @Select_Command_Temp = Right(@Select_Command_Temp,Len(@Select_Command_Temp) - 7)
---取各保留字位置，以便获得表的列表
Select @From_Pos = CHARINDEX(' from ',@Select_Command_Temp)
Select @Where_Pos = CHARINDEX(' where ',@Select_Command_Temp)
Select @Having_Pos = CHARINDEX(' having ',@Select_Command_Temp)
Select @Groupby_Pos = CHARINDEX(' groupby ',@Select_Command_Temp)
Select @Orderby_Pos = CHARINDEX(' orderby ',@Select_Command_Temp)

If @Where_Pos > 0 Select @Temp_Pos = @Where_Pos
If @Having_Pos > 0 And @Having_Pos < @Temp_Pos Select @Temp_Pos = @Having_Pos
If @Groupby_Pos > 0 And @Groupby_Pos < @Temp_Pos Select @Temp_Pos = @Groupby_Pos
If @Orderby_Pos > 0 And @Orderby_Pos < @Temp_Pos Select @Temp_Pos = @Orderby_Pos
---取表列表
If @Temp_Pos > 0
   Begin
   Select @Table_List = SUBSTRING(@Select_Command_Temp,@From_Pos + 6 ,@Temp_Pos - @From_Pos - 1)
   End
Else
   Begin
   Select @Table_List = SUBSTRING(@Select_Command_Temp,@From_Pos + 6 ,Len(@Select_Command_Temp) - @From_Pos - 1)
   End

Select @Column_Syntax = ''
---只列出栏位
Select @Select_Command_Temp = Left(@Select_Command_Temp,@From_Pos - 1)
While Len(@Select_Command_Temp) > 0
   Begin
   ---取逗号位置
   Select @Temp_Pos = CHARINDEX(',',@Select_Command_Temp)
   ---初次取栏位名称
   If @Temp_Pos > 0
      Begin
      Select @Column_Name = Left(@Select_Command_Temp,@Temp_Pos - 1)
      End
   Else
      Begin
      Select @Column_Name = @Select_Command_Temp
      End
   ---取表名和栏位名（可能是‘*’）
   If CHARINDEX('.',@Column_Name) > 0
      Begin
      Select @Table_Name = Left(@Column_Name,CHARINDEX('.',@Column_Name) - 1)
      Select @Column_Name = Right(@Column_Name,Len(@Column_Name) - CHARINDEX('.',@Column_Name))
      End
   Else
      Begin
      Select @Table_Name = @Table_List
      End

   ---栏位出现'*'
   If CHARINDEX('*',@Column_Name) > 0
      Begin
      Select @Column_Name = ''
      Select @Loop_Seq = 1
      ---取栏位个数
      Select @Column_Count = Count(*)
        From SysColumns
       Where Id = Object_Id(@Table_name)
      While @Loop_Seq <= @Column_Count
         Begin
         ---取栏位名称,栏位类型，长度，精度，小数位
         Select @Column_Name_Temp = SysColumns.Name,
                @Column_Type_Temp = Lower(SysTypes.Name),
                @Column_Length_Temp = SysColumns.Length,
                @Column_Xprec_Temp = SysColumns.Xprec,
                @Column_Xscale_Temp = SysColumns.Xscale
           From SysColumns,SysTypes
          Where SysColumns.Id = Object_Id(@Table_name) And
                SysColumns.Colid = @Loop_Seq And
                SysColumns.XuserType = SysTypes.XuserType
         ---形成栏位语法表达式
         Select @Column_Syntax_Temp = Case When @Column_Type_Temp In ('datetime','image','int') Then @Column_Name_Temp + ' ' + @Column_Type_Temp
                                           When @Column_Type_Temp In ('binary','bit','char','varchar') Then @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(Varchar(10),@Column_Length_Temp) + ')'
                                           Else @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(varchar(10),@Column_Xprec_Temp) + ',' + Convert(varchar(10),@Column_Xscale_Temp) + ')'
                                      End
         Select @Column_Syntax = @Column_Syntax + @Column_Syntax_Temp + ','
         Select @Loop_Seq = @loop_Seq + 1
         End
      End
   Else
      Begin
      ---取栏位名称
      Select @Column_Name_Temp = @Column_Name
      ---取栏位类型，长度，精度，小数位
      Select @Column_Type_Temp = Lower(SysTypes.Name),
             @Column_Length_Temp = Isnull(SysColumns.Length,0),
             @Column_Xprec_Temp = Isnull(SysColumns.Xprec,0),
             @Column_Xscale_Temp = Isnull(SysColumns.Xscale,0)
        From SysColumns,SysTypes
       Where SysColumns.Id = Object_Id(@Table_name) And
             SysColumns.Name = @Column_Name_Temp And
             SysColumns.XuserType = SysTypes.XuserType
      ---形成栏位语法表达式
      Select @Column_Syntax_Temp = Case When @Column_Type_Temp In ('datetime','image','int') Then @Column_Name_Temp + ' ' + @Column_Type_Temp
                                        When @Column_Type_Temp In ('binary','bit','char','varchar') Then @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(Varchar(10),@Column_Length_Temp) + ')'
                                        Else @Column_Name_Temp + ' ' + @Column_Type_Temp + '('+Convert(varchar(10),@Column_Xprec_Temp) + ',' + Convert(varchar(10),@Column_Xscale_Temp) + ')'
                                   End
      Select @Column_Syntax = @Column_Syntax + @Column_Syntax_Temp + ','

      End
      ---处理栏位列表
      If @Temp_Pos > 0
         Begin
         Select @Select_Command_Temp = Right(@Select_Command_Temp,Len(@Select_Command_Temp) - @Temp_Pos)
         End
      Else
         Begin
         Select @Select_Command_Temp = ''
         End
   End
   ---形成正确的栏位创建语法
   Select @Column_Syntax = Left(@Column_Syntax,Len(@Column_Syntax) - 1)
   ---修改临时表的结构
   Execute('Alter Table #Test Add '+@Column_Syntax)
   Execute('Alter Table #Test Drop Column a')
   ---将SELECT执行的结构集插入到临时表
   Insert Into #Test
   Execute(@Select_Command)
   ---创建游标
   Set @Cursor_Return =  CURSOR LOCAL SCROLL READ_ONLY FOR
                         Select *
                           From #Test       
   ---打开游标                
   Open @Cursor_Return

 

▲使用游标

/注:在SELECT中有几项,fetch from @cursor_name into @cust_id就应该声明几个变量,而且顺序和类型必须一致.*/
declare @cursor_name cursor,
        @select_command varchar(8000),
        @cust_id varchar(20)
select @select_command = 'select cust_id from so_cust'
execute usp_createcursor @select_command,@cursor_name OUTPUT
fetch from @cursor_name into @cust_id
while @@fetch_status = 0
   begin
   fetch from @cursor_name into @cust_id
   end
close @cursor_name
deallocate cursor_name

说明:上述代码在MSS SQL SERVER7.0上通过。其它数据库只需修改一下抓取栏位及其类型的系统表就可以了。