Oracle嵌套游标

Question

I want to get the distinct dates in a column called "YMDH" from each table in a schema where that column exists. I figured that I needed to use nested cursors (something I've not done before) and came up with the following code:

CREATE OR REPLACE PROCEDURE DistinctDates AS 
   sql_statement1 varchar2(200);
   sql_statement2 varchar2(200);
   results varchar2(15);
   ColumnExist integer;
BEGIN
    for cursor_rec in (SELECT * FROM user_objects WHERE object_type='TABLE'
    AND object_name NOT LIKE 'TM%')  loop
    sql_statement1 := 'select count (*) from user_tab_columns where table_name=' || '''' || cursor_rec.object_name || '''' || ' and column_name=' || '''' ||'YMDH'  || '''';
    execute immediate sql_statement1 into ColumnExist;
    if ColumnExist = 1 then
      for inner_cursor_rec in (select distinct(ymdh) from cursor_rec.object_name) loop
         null;
      end loop;
    end if;
    end loop;
END DistinctDates;

SQL Developer is complaining about the select statement for the inner cursor. The error message is:

Error(18,32): PL/SQL: SQL Statement ignored Error(18,70): PL/SQL: ORA-00942: table or view does not exist

So it's not recognizing the reference to the outer cursor. How do I pass the table name (which is the cursor_rec.object_name) to the inner cursor?

Answer 1

You have used dynamic SQL where it is not needed, and have not used it where it is needed!

The check to see if the table has a column called 'YMDH' can be incorporated into the first query, giving this code:

CREATE OR REPLACE PROCEDURE DistinctDates AS 
   sql_statement varchar2(200);
   rc sys_refcursor;
   ymdh_value ????; -- Appropriate data type
BEGIN
    for cursor_rec in (SELECT t.table_name 
                       FROM user_tables t
                       JOIN user_tab_columns c ON c.table_name = t.table_name
                       WHERE t.table_name NOT LIKE 'TM%'
                       AND c.column_name='YMDH')  
    loop
        sql_statement := 'select distinct(ymdh) from ' || cursor_rec.table_name;
        open rc for sql_statement;
        loop
            fetch rc into ymdh_value;
            exit when rc%notfound;
            null;
        end loop;
        close rc;
    end loop;
END DistinctDates;