Oracle - 从引用游标中选择特定的列 [英] Oracle - select a specific column from a ref cursor

问题描述

我有一个名为Table1的表。它有很多列，其中一个是Column1。我不知道其他列，他们甚至可能改变有时。有一个强类型的ref游标类型，返回Table1％rowtype，命名为cur_Table1。我有一个名为SP1的存储过程，它的out参数类型为cur_Table1。我从另一个只看到此存储过程的数据库调用此SP1存储过程，但不调用表或类型本身。如何从返回的游标中仅选择Column1？我知道我可以抓取一个记录或尽可能多的变量，因为游标有列，但我只知道一列的存在，所以我不能声明完整的记录或正确数量的变量。

<你可以用 DBMS_SQL 来做到这一点，但它不漂亮。

表格和示例数据（COLUMN1的数字为1 - 10）：

  create table table1（column1 number，column2 date，column3 varchar2（1000），column4 clob）; 
 
 insert into table1 
 select level，sysdate，level，level from dual connect by level< = 10; 
 commit; 
  

使用打开引用游标并选择所有内容的过程的包： / p>

 创建或替换包test_pkg是
类型cur_Table1是ref游标返回table1％rowtype; 
 procedure sp1（p_cursor in out cur_table1）; 
 end; 
 / 
 
创建或替换包主体test_pkg是
过程sp1（p_cursor在外部cur_table1中）是
 begin 
为选择column1，column2打开p_cursor， column3，column4 from table1; 
 end; 
 end; 
 / 
  

从引用游标读取COLUMN1数据的PL / SQL块：

   - 基本步骤是：调用过程，转换光标，描述和查找列，
  -  - 然后提取行并检索列值。 
  -  
  - 需要在此处添加COLUMN1的每种可能的数据类型。 
  - 目前只支持NUMBER。 
 declare 
 v_cursor sys_refcursor; 
 v_cursor_number number; 
 
 v_columns number; 
 v_desc_tab dbms_sql.desc_tab; 
 v_position number; 
 v_typecode number; 
 v_number_value number; 
 begin 
  - 打开游标的调用过程
 test_pkg.sp1（v_cursor）; 
  - 将游标转换为DBMS_SQL游标
 v_cursor_number：= dbms_sql.to_cursor_number（rc => v_cursor）; 
  - 获取列上的信息
 dbms_sql.describe_columns（v_cursor_number，v_columns，v_desc_tab）; 
 
  - 遍历所有列，找到COLUMN1位置并键入
 for i in 1 .. v_desc_tab.count循环
如果v_desc_tab（i）.col_name ='COLUMN1'那么
 v_position：= i; 
 v_typecode：= v_desc_tab（i）.col_type; 
 
  - 选择要选择的COLUMN1。 
 if v_typecode = dbms_types.typecode_number then 
 dbms_sql.define_column（v_cursor_number，i，v_number_value）; 
 --...对每种可能的类型重复。 
 end if; 
 end if; 
 end loop; 
 
  - 获取所有行，然后获取相关的列值并打印
，而dbms_sql.fetch_rows（v_cursor_number）> 0 loop 
 if v_typecode = dbms_types.typecode_number then 
 dbms_sql.column_value（v_cursor_number，v_position，v_number_value）; 
 dbms_output.put_line（'Value：'|| v_number_value）; 
 --...对每个可能的类型重复
 end if; 
 end loop; 
 end; 
 / 
  

I have a table named Table1. It has lots of columns, one of them is Column1. I don't know the other columns, they may even change sometimes. There is a strongly typed ref cursor type which returns Table1%rowtype, named cur_Table1. I have a stored procedure named SP1 which has an out parameter of type cur_Table1. I'm calling this SP1 stored procedure from another database that only sees this stored procedure, but not the table or the type itself. How do I select only Column1 from the returned cursor? I know I can fetch into a record or as many variables as the cursor has columns, but I only know of one column's existence so I can't declare the complete record or correct number of variables.

解决方案

You can do this with DBMS_SQL, but it ain't pretty.

Table and sample data (COLUMN1 has the numbers 1 - 10):

create table table1(column1 number, column2 date, column3 varchar2(1000), column4 clob);

insert into table1
select level, sysdate, level, level from dual connect by level <= 10;
commit;

Package with a procedure that opens a ref cursor and selects everything:

create or replace package test_pkg is
    type cur_Table1 is ref cursor return table1%rowtype;
    procedure sp1(p_cursor in out cur_table1);
end;
/

create or replace package body test_pkg is
    procedure sp1(p_cursor in out cur_table1) is
    begin
        open p_cursor for select column1, column2, column3, column4 from table1;
    end;
end;
/

PL/SQL block that reads COLUMN1 data from the ref cursor:

--Basic steps are: call procedure, convert cursor, describe and find columns,
--then fetch rows and retrieve column values.
--
--Each possible data type for COLUMN1 needs to be added here.
--Currently only NUMBER is supported.
declare
    v_cursor sys_refcursor;
    v_cursor_number number;

    v_columns number;
    v_desc_tab dbms_sql.desc_tab;
    v_position number;
    v_typecode number;
    v_number_value number;
begin
    --Call procedure to open cursor
    test_pkg.sp1(v_cursor);
    --Convert cursor to DBMS_SQL cursor
    v_cursor_number := dbms_sql.to_cursor_number(rc => v_cursor);
    --Get information on the columns
    dbms_sql.describe_columns(v_cursor_number, v_columns, v_desc_tab);

    --Loop through all the columns, find COLUMN1 position and type
    for i in 1 .. v_desc_tab.count loop
        if v_desc_tab(i).col_name = 'COLUMN1' then
            v_position := i;
            v_typecode := v_desc_tab(i).col_type;

            --Pick COLUMN1 to be selected.
            if v_typecode = dbms_types.typecode_number then
                dbms_sql.define_column(v_cursor_number, i, v_number_value);
            --...repeat for every possible type.
            end if;
        end if;
    end loop;

    --Fetch all the rows, then get the relevant column value and print it
    while dbms_sql.fetch_rows(v_cursor_number) > 0 loop
        if v_typecode = dbms_types.typecode_number then
            dbms_sql.column_value(v_cursor_number, v_position, v_number_value);
            dbms_output.put_line('Value: '||v_number_value);
        --...repeat for every possible type
        end if;
    end loop;   
end;
/

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