使用流水线函数从多表join获取结果集。

Posted 2021-03-19

我想创建一个函数来获取表的选择性，输入参数是所有者和表名，我搜索了一下，发现这里可以使用pipelined函数，我使用了下面的代码，但我创建函数时出现了错误。

create or replace type ROW_TYPE as object
(
 column_name varchar2(128),
 num_rows number,
 num_distinct number
);
/

create or replace type TABLE_TYPE as table of ROW_TYPE;
/

create or replace function getSelectivity(owner in varchar2, tab_name in varchar2)
return TABLE_TYPE
PIPELINED
IS
BEGIN
 for myrow in(
             select a.column_name,b.num_rows,a.num_distinct
             from dba_tab_col_statistics a, dba_tables b
             where a.owner = b.owner and a.table_name = b.table_name and a.owner=upper(owner) and 
a.table_name =upper(tab_name)
 )loop

pipe row(ROW_TYPE(myrow.column_name,myrow.num_rows,myrow.num_distinct));
end loop;
return;
end;
/

错误：

SQL> show errors;
Errors for FUNCTION MOVIL.GETSELECTIVITY:
LINE/COL ERROR
-------- -------------------------------
9/88     PL/SQL: ORA-00918: undefined column
7/14     PL/SQL: SQL Statement ignored
12/20    PLS-00364: Invalid usage of Loop index variable 'MYROW'
12/2     PL/SQL: Statement ignored

但如果我只查询一张表，那么一切都很好。

create or replace type ROW_TYPE as object
(
 column_name varchar2(128),
 num_distinct number
);
/

create or replace type TABLE_TYPE as table of ROW_TYPE;
/

create or replace function getSelectivity(owner in varchar2, tab_name in varchar2)
return TABLE_TYPE
PIPELINED
IS
BEGIN
 for myrow in(
             select a.column_name,a.num_distinct
             from dba_tab_col_statistics a
             where a.owner=upper(owner) and a.table_name =upper(tab_name)
 )loop

 pipe row(ROW_TYPE(myrow.column_name,myrow.num_distinct));
 end loop;
 return;
 end;
/

pipelined函数不支持多表连接吗？

答案

你可以创建一个像下面这样的表的视图，并在你的函数中使用它。

       create  or replace view test_db_view as  select 
         a.column_name,b.num_rows,a.num_distinct,
         a.table_name,a.owner
         from all_tab_col_statistics a, all_tables b
         where a.owner = b.owner and a.table_name = b.table_name


   create or replace function getSelectivity(owner in varchar2, tab_name in varchar2)
    return TABLE_TYPE
    PIPELINED
    IS
    BEGIN
     for myrow in( select * from test_db_view a where a.owner=upper(owner) and 
    a.table_name =upper(tab_name)


     )loop

    pipe row(ROW_TYPE(myrow.column_name,myrow.num_rows,myrow.num_distinct));
    end loop;
    return;
    end;

或者你可以尝试使用 p_owner 而不是 owner 按功能 getSelectivity 参数