EXTERNAL TABLE ACCESS (SAMPLE)

Description

Select a sample of rows from an external table

Versions

This operation was introduced in Oracle 9.0.1

This operation is implemented in the following versions

This operation has not yet been reproduced in Oracle 10.2

Example

This example was developed using Oracle 9.2.0.1 on Windows 2000

This example requires a directory

    CREATE DIRECTORY d000 AS "pathname";

The directory does not need to be added to the utl_file_dir parameter

Create a file within the directory e.g.

    SET FEEDBACK OFF
    SET TRIMSPOOL ON
    SET SERVEROUTPUT ON
    SPOOL t1.csv
    BEGIN
      dbms_output.enable (100000);

      FOR f IN 0..99
      LOOP
        dbms_output.put_line (f||','||LPAD (TO_CHAR (f),10,'0'));
      END LOOP;
    END;
    /

    SPOOL OFF

Create a table definition

    CREATE TABLE t1 
    (
      c1 NUMBER, 
      c2 VARCHAR2(10)
    )
    ORGANIZATION EXTERNAL
    (
      TYPE ORACLE_LOADER
      DEFAULT DIRECTORY d000
      ACCESS PARAMETERS
      (
        RECORDS DELIMITED BY NEWLINE
        FIELDS TERMINATED BY ','
        (
          c1 CHAR,
          c2 CHAR
        )
      )
      LOCATION ('t1.csv');
    );

The statement

    SELECT * FROM t1 SAMPLE (10);

generates the following execution plan

0     SELECT STATEMENT Optimizer=CHOOSE
1   0   EXTERNAL TABLE ACCESS (SAMPLE) OF 'T1'

In Oracle 10.2 the statement

    SELECT * FROM t1 SAMPLE (10);

generates the following error message

    30560, 00000, "SAMPLE clause not allowed"