Identify a table with maximum rows in Oracle

Question

I have a set of tables in Oracle and I would like to identify the table that contains the maximum number of rows.

So if, A has 200 rows, B has 345 rows and C has 120

Answer 1

Here's another method, likely to be much slower than simply getting ALL_TABLES.NUM_ROWS, but it doesn't depend on statistics having been gathered and gives exact, current values -- although how current depends on how long it takes to run!

-- For running in SQLPlus you need this to see the output.
-- If running in Toad or similar tool, output is enabled by default

    SET SERVEROUTPUT ON SIZE 100000

    DECLARE
      l_rows  INTEGER;
      l_max_rows  INTEGER := 0;
      l_table_name  all_tables.table_name%TYPE := NULL;
    BEGIN
      FOR table_record IN (SELECT table_name FROM all_tables) LOOP

        EXECUTE IMMEDIATE 'SELECT COUNT(*) FROM '||table_record.table_name
          INTO l_rows;

        IF l_rows > l_max_rows THEN
          l_max_rows := l_rows;
          l_table_name := table_record.table_name;
        END IF;
      END LOOP;

      IF l_table_name IS NULL THEN
        dbms_output.put_line( 'All tables are empty' );
      ELSE
        dbms_output.put_line( 'Table ' || table_record.table_name || 
                              ' has ' || TO_CHAR(l_max_rows) || ' rows'
                            );
      END IF;
    END;
    /