Example 19-1 Using ORACLE_LOADER to Create a Partitioned External Table

This example assumes there are four data files with the following content:

p1a.dat:
1, AAAAA Plumbing,01372,
28, Sparkly Laundry,78907,
13, Andi's Doughnuts,54570,

p1b.dat:
51, DIY Supplies,61614,
87, Fast Frames,22201,
89, Friendly Pharmacy,89901,

p2.dat:
121, Pleasant Pets,33893,
130, Bailey the Bookmonger,99915,
105, Le Bistrot du Chat Noir,94114,

p3.dat:
210, The Electric Eel Diner,07101,
222, Everyt'ing General Store,80118,
231, Big Rocket Market,01754,

There are three fields in the data file: CUSTOMER_NUMBER, CUSTOMER_NAME and POSTAL_CODE.  The external table uses range partitioning on CUSTOMER_NUMBER to create three partitions.

• Partition 1 is for customer_number less than 100

• Partition 2 is for customer_number less than 200

• Partition 3 is for customer_number less than 300

Note that the first partition has two data files while the other partitions only have one. The following is the output from SQLPlus for creating the file.

SQL> create table customer_list_xt
  2    (CUSTOMER_NUMBER number, CUSTOMER_NAME VARCHAR2(50), POSTAL_CODE CHAR(5))
  3  organization external
  4    (type oracle_loader default directory def_dir1)
  5  partition by range(CUSTOMER_NUMBER)
  6  (
  7    partition p1 values less than (100) location('p1a.dat', 'p1b.dat'),
  8    partition p2 values less than (200) location('p2.dat'),
  9    partition p3 values less than (300) location('p3.dat')
 10  );

Table created.
SQL> 

The following is the output from SELECT * for the entire table:

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_xt
  3    order by customer_number;

CUSTOMER_NUMBER CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
              1  AAAAA Plumbing                                    01372
             13  Andi's Doughnuts                                  54570
             28  Sparkly Laundry                                   78907
             51  DIY Supplies                                      61614
             87  Fast Frames                                       22201
             89  Friendly Pharmacy                                 89901
            105  Le Bistrot du Chat Noir                           94114
            121  Pleasant Pets                                     33893
            130  Bailey the Bookmonger                             99915
            210  The Electric Eel Diner                            07101
            222  Everyt'ing General Store                          80118
            231  Big Rocket Market                                 01754

12 rows selected.

SQL> 

The following query should only read records from the first partition:

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_xt
  3    where customer_number < 20
  4    order by customer_number;

CUSTOMER_NUMBER CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
              1  AAAAA Plumbing                                    01372
             13  Andi's Doughnuts                                  54570

2 rows selected.

SQL> 

The following query specifies the partition to read as part of the SELECT statement.

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_xt partition (p1)
  3    order by customer_number;

CUSTOMER_NUMBER CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
              1  AAAAA Plumbing                                    01372
             13  Andi's Doughnuts                                  54570
             28  Sparkly Laundry                                   78907
             51  DIY Supplies                                      61614
             87  Fast Frames                                       22201
             89  Friendly Pharmacy                                 89901

6 rows selected.

SQL> 

Example 19-2 Example

Here is an example of a statement for creating a partitioned hybrid l table:

CREATE TABLE hybrid_pt (time_id date, customer number)
  TABLESPACE TS1
  EXTERNAL PARTITION ATTRIBUTES (TYPE ORACLE_LOADER 
                                 DEFAULT DIRECTORY data_dir0
                                 ACCESS PARAMETERS(FIELDS TERMINATED BY ',')
                                 REJECT LIMIT UNLIMITED) 
PARTITION by range (time_id)
(
 PARTITION century_18 VALUES LESS THAN ('01-01-1800')
    EXTERNAL,                                                 <-- empty external partition
  PARTITION century_19 VALUES LESS THAN ('01-01-1900')
    EXTERNAL DEFAULT DIRECTORY data_dir1 LOCATION (‘century19_data.txt'),
  PARTITION century_20 VALUES LESS THAN ('01-01-2000') 
    EXTERNAL LOCATION (‘century20_data.txt'),
  PARTITION year_2000 VALUES LESS THAN ('01-01-2001') TABLESPACE TS2,
  PARTITION pmax VALUES LESS THAN (MAXVALUE)
);

In this example, the table contains both internal and external partitions. The default tablespace for internal partitions in the table is TS1. An EXTERNAL PARTITION ATTRIBUTES clause is added for specifying parameters that apply, at the table level, to the external partitions in the table. The clause is mandatory for hybrid partitioned tables. In this case, external partitions are accessed through the ORACLE_LOADER access driver, and the parameters required by the access driver are specified in the clause. At the partition level, an EXTERNAL clause is specified in each external partition, along with any external parameters applied to the partition.

In this example, century_18, century_19, and century_20 are external partitions. century_18 is an empty partition since it does not contain a location. The default directory for partition century_19 isdata_dir1, overriding the table level default directory. The partition has a location data_dir1:century19_data.txt. Partitioncentury_20 has location data_dir0:century20_data.txt, since the table level default directory is applied to a location when a default directory is not specified in a partition. Partitions year_2000 and pmax are internal partitions. Partition year_2000has a tablespace TS2. When a partition has noEXTERNAL clause or external parameters specified in it, it is assumed to be an internal partition by default.

Example 19-3 Using the ORACLE_DATAPUMP Access Driver to Create Partitioned External Tables

In this example, the dump files used are the same as those created in the previous example using the ORACLE_LOADER access driver. However, in this example, in addition to partitioning the data using customer_number, the data is subpartitioned using postal_code.  For every partition, there is a subpartition where the postal_code is less than 50000 and another subpartition for all other values of postal_code.  With three partitions, each containing two subpartitions, a total of six files is required. To create the files, use the SQL CREATE TABLE AS SELECT statement to select the correct rows for the partition and then write those rows into the file for the ORACLE_DATAPUMP driver.

The following statement creates a file with data for the first subpartition (postal_code less than 50000) of partition p1 (customer_number less than 100).

SQL> create table customer_list_dp_p1_sp1_xt
  2  organization external
  3    (type oracle_datapump default directory def_dir1 location('p1_sp1.dmp'))
  4  as
  5    select customer_number, customer_name, postal_code
  6      from customer_list_xt partition (p1)
  7      where to_number(postal_code) < 50000;

Table created.

SQL> 

This statement creates a file with data for the second subpartition (all other values for postal_code) of partition p1 (customer_number less than 100).

SQL> create table customer_list_dp_p1_sp2_xt
  2  organization external
  3    (type oracle_datapump default directory def_dir1 location('p1_sp2.dmp'))
  4  as
  5    select customer_number, customer_name, postal_code
  6      from customer_list_xt partition (p1)
  7      where to_number(postal_code) >= 50000;

Table created. 

The files for other partitions are created in a similar fashion, as follows:

SQL> create table customer_list_dp_p2_sp1_xt
  2  organization external
  3    (type oracle_datapump default directory def_dir1 location('p2_sp1.dmp'))
  4  as
  5    select customer_number, customer_name, postal_code
  6      from customer_list_xt partition (p2)
  7      where to_number(postal_code) < 50000;

Table created.

SQL>
SQL> create table customer_list_dp_p2_sp2_xt
  2  organization external
  3    (type oracle_datapump default directory def_dir1 location('p2_sp2.dmp'))
  4  as
  5    select customer_number, customer_name, postal_code
  6      from customer_list_xt partition (p2)
  7      where to_number(postal_code) >= 50000;

Table created.

SQL>
SQL> create table customer_list_dp_p3_sp1_xt
  2  organization external
  3    (type oracle_datapump default directory def_dir1 location('p3_sp1.dmp'))
  4  as
  5    select customer_number, customer_name, postal_code
  6      from customer_list_xt partition (p3)
  7      where to_number(postal_code) < 50000;

Table created.

SQL>
SQL> create table customer_list_dp_p3_sp2_xt
  2  organization external
  3    (type oracle_datapump default directory def_dir1 location('p3_sp2.dmp'))
  4  as
  5    select customer_number, customer_name, postal_code
  6      from customer_list_xt partition (p3)
  7      where to_number(postal_code) >= 50000;

Table created.

SQL>

You can select from each of these external tables to verify that it has the data you intended to write out.  After you have executed the SQL CREATE TABLE AS SELECT statement, you can drop these external tables.

To use a virtual column to partition the table, create the partitioned ORACLE_DATAPUMP table.  Again, the table is partitioned on the customer_number column and subpartitioned on the postal_code column. The postal_code column is a character field that contains numbers, but this example partitions it based on the numeric value, not a character string.  In order to do this, create a virtual column, postal_code_num, whose value is the postal_code field converted to a NUMBER data type.  The SUBPARTITION clause uses the virtual column to determine the subpartition for the row.

SQL> create table customer_list_dp_xt
  2  (customer_number    number,
  3   CUSTOMER_NAME      VARCHAR2(50),
  4   postal_code        CHAR(5),
  5   postal_code_NUM    as (to_number(postal_code)))
  6  organization external
  7    (type oracle_datapump default directory def_dir1)
  8  partition by range(customer_number)
  9  subpartition by range(postal_code_NUM)
 10  (
 11    partition p1 values less than (100)
 12     (subpartition p1_sp1 values less than (50000) location('p1_sp1.dmp'),
 13      subpartition p1_sp2 values less than (MAXVALUE) location('p1_sp2.dmp')),
 14    partition p2 values less than (200)
 15     (subpartition p2_sp1 values less than (50000) location('p2_sp1.dmp'),
 16      subpartition p2_sp2 values less than (MAXVALUE) location('p2_sp2.dmp')),
 17    partition p3 values less than (300)
 18     (subpartition p3_sp1 values less than (50000) location('p3_sp1.dmp'),
 19      subpartition p3_sp2 values less than (MAXVALUE) location('p3_sp2.dmp'))
 20  );

Table created.

SQL> 

If you select all rows, then the data returned is the same as was returned in the previous example using the ORACLE_LOADER access driver.

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_dp_xt
  3    order by customer_number;

customer_number CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
              1  AAAAA Plumbing                                    01372
             13  Andi's Doughnuts                                  54570
             28  Sparkly Laundry                                   78907
             51  DIY Supplies                                      61614
             87  Fast Frames                                       22201
             89  Friendly Pharmacy                                 89901
            105  Le Bistrot du Chat Noir                           94114
            121  Pleasant Pets                                     33893
            130  Bailey the Bookmonger                             99915
            210  The Electric Eel Diner                            07101
            222  Everyt'ing General Store                          80118
            231  Big Rocket Market                                 01754

12 rows selected.

SQL> 

The WHERE clause can limit the rows read to a subpartition. The following query should only read the first subpartition of the first partition.

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_dp_xt
  3    where customer_number < 20 and postal_code_NUM < 39998
  4    order by customer_number;

customer_number CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
              1  AAAAA Plumbing                                    01372

1 row selected.

SQL> 

You could also specify a specific subpartition in the query, as follows:

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_dp_xt subpartition (p2_sp2) order by customer_number;

customer_number CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
            105  Le Bistrot du Chat Noir                           94114
            130  Bailey the Bookmonger                             99915

2 rows selected.

SQL> 

Example 19-4 Using the ORACLE_HDFS Access Driver to Create Partitioned External Tables

In this example there are four data files stored in HDFS directory path "hdfs_pet/". 

p1a.dat
1, AAAAA Plumbing,01372,
28, Sparkly Laundry,07101,
13, Andi'''s Doughnuts,01372,

p1b.dat
51, DIY Supplies,07101,
87, Fast Frames,01754,
89, Friendly Pharmacy,01372,

p2.dat
121, Pleasant Pets,01754,
130, Bailey the Bookmonger,01754,
105, Le Bistrot du Chat Noir,01754,

p3.dat
210, The Electric Eel Diner,07101,
222, Everyt'ing General Store,01372,
231, Big Rocket Market,01754,

For the purposes of this example, the data files are written to the HDFS directory using the following:

hadoop dfs -mkdir hdfs_pet
hadoop dfs -put p1a.dat hdfs_pet/p1a.dat
hadoop dfs -put p1b.dat hdfs_pet/p1b.dat
hadoop dfs -put p2.dat hdfs_pet/p2.dat
hadoop dfs -put p3.dat hdfs_pet/p3.dat

The following is the CREATE TABLE command to create the partitioned external table:

create table customer_list_hdfs
  (CUSTOMER_NUMBER number, CUSTOMER_NAME VARCHAR2(50), POSTAL_CODE CHAR(5))
organization external
  (type oracle_hdfs
   default directory def_dir1
   access parameters
   (com.oracle.bigdata.cluster   = hadoop_cl_1
    com.oracle.bigdata.rowformat = delimited fields terminated by ','))
partition by range(CUSTOMER_NUMBER)
(
  partition p1 values less than (100) location('hdfs_pet/p1a.dat', 'hdfs_pet/p1b.dat'),
  partition p2 values less than (200) location('hdfs_pet/p2.dat'),
  partition p3 values less than (300) location('hdfs_pet/p3.dat')
); 

The following query shows a SELECT operation from the external table:

SQL> select * from customer_list_hdfs order by customer_number;

CUSTOMER_NUMBER CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
              1  AAAAA Plumbing                                    01372
             13  Andi's Doughnuts                                  01372
             28  Sparkly Laundry                                   07101
             51  DIY Supplies                                      07101
             87  Fast Frames                                       01754
             89  Friendly Pharmacy                                 01372
            105  Le Bistrot du Chat Noir                           01754
            121  Pleasant Pets                                     01754
            130  Bailey the Bookmonger                             01754
            210  The Electric Eel Diner                            07101
            222  Everyt'ing General Store                          01372
            231  Big Rocket Market                                 01754

12 rows selected.

SQL> 

You can also execute queries with a WHERE clause that excludes partitions that cannot match the conditions in the WHERE clause from being read, as follows:

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_hdfs
  3    where customer_number < 20
  4    order by customer_number;

CUSTOMER_NUMBER CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
              1  AAAAA Plumbing                                    01372
             13  Andi's Doughnuts                                  01372

2 rows selected.

SQL> 

You could also specify the partition you want to read as part of the FROM clause, as shown in the following:

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_hdfs partition (p3)
  3    order by customer_number;

CUSTOMER_NUMBER CUSTOMER_NAME                                      POSTA
--------------- -------------------------------------------------- -----
            210  The Electric Eel Diner                            07101
            222  Everyt'ing General Store                          01372
            231  Big Rocket Market                                 01754

3 rows selected.

SQL> 

Example 19-5 Using the ORACLE_HIVE Access Driver to Create Partitioned External Tables

This examples creates the Hive table using the data files from the previous example showing how to use ORACLE_HDFS to create partitioned external tables.. The following commands are all performed inside of the Hive CLI so they use Hive syntax.

First, use Hive to create a Hive external table on top of the HDFS data files, as follows:

create external table customer_list_no_part ( customer_number int,
                                              customer_name   string,
                                              postal_code string)
 row format delimited fields terminated by ','
 stored as textfile
 location '/user/doc/hdfs_pet'

Then execute the following commands to tell Hive to create the partitions dynamically:

set hive.exec.dynamic.partition=true
set hive.exec.dynamic.partition.mode=nonstrict

Create the partitioned Hive table:

create table customer_list( CUSTOMER_NUMBER int,
                            CUSTOMER_NAME   string)
 partitioned by (postal_code string)
 row format delimited
 fields terminated by '\t'
 location '/user/doc/doc_pet'

Populate the hive table with data from table customer_list_no_part.  This should create the files for each partition with the correct rows.

insert overwrite table customer_list partition (postal_code) select * from customer_list_no_part

The Hive customer_list table is populated with the rows. as shown in the following query:

select * from customer_list order by customer_number
1     AAAAA Plumbing    01372
13     Andi's Doughnuts    01372
28     Sparkly Laundry    07101
51     DIY Supplies    07101
87     Fast Frames    01754
89     Friendly Pharmacy    01372
105     Le Bistrot du Chat Noir    01754
121     Pleasant Pets    01754
130     Bailey the Bookmonger    01754
210     The Electric Eel Diner    07101
222     Everyt'ing General Store    01372
231     Big Rocket Market    01754

Now you can go back to SQL*Plus to create the partitioned external table inside the Oracle database. First, use PL/SQL function DBMS_HADOOP.CREATE_EXTDDL_FOR_HIVE() to create the external table. The arguments are as follows:

1. the name of the Hadoop cluster

2. the name of the Hive user that owns the table

3. the name of the partitioned Hive table

4. a boolean value indicating whether you want the partition columns in the Hive table to be included as columns in the external table

5. the name of the partitioned ORACLE_HIVE table that is created

6. a boolean value indicating whether the CREATE DDL is executed

7. a CLOB contains the CREATE DDL string

This example gets the CLOB for the CREATE DDL string and uses the DBMS_OUTPUT.PUT_LINE() procedure to write it.  Setting SERVEROUTPUT ON tells SQL*Plus to display the data from the DBMS_OUTPUT.PUT_LINE() procedure.  Setting LINESIZE to 132 makes sure there are no line breaks at odd places when displaying the data from the DBMS_OUTPUT.PUT_LINE() procedure.

SQL> SET LINESIZE 132
SQL> SET SERVEROUTPUT ON
SQL>
SQL> DECLARE
  2    DDLtxt clob;
  3  BEGIN
  4    dbms_hadoop.create_extddl_for_hive
  5     ('hadoop_cl_1', 'default', 'customer_list',
  6      TRUE, 'CUSTOMER_LIST_HIVE', TRUE, DDLtxt);
  7    dbms_output.put_line('DDL Text is :  ' || DDLtxt);
  8  END;
  9  /
External table successfully created.
DDL Text is :  CREATE TABLE "DOC"."CUSTOMER_LIST_HIVE" (customer_number NUMBER, customer_name VARCHAR2(4000), postal_code
VARCHAR2(4000))  ORGANIZATION EXTERNAL
 (TYPE ORACLE_HIVE
 DEFAULT DIRECTORY DEFAULT_DIR
 ACCESS PARAMETERS
(
com.oracle.bigdata.cluster=hadoop_cl_1
com.oracle.bigdata.tablename=default.customer_list)
) REJECT LIMIT UNLIMITED
PARTITION BY
LIST (postal_code)
(
PARTITION "P_293620257" VALUES ('01372'),
PARTITION "P_292175793" VALUES ('01754'),
PARTITION "P_717839126"
VALUES ('07101')
)

Because Hive does not specify a maximum character count for STRING columns, the column definition for the external table is VARCHAR2(4000).  If you want a smaller length for some columns, you can call the DBMS_HADOOP.CREATE_EXTDDL_FOR_HIVE() procedure and specify that you do not want to execute the CREATE DDL.  Then, you can edit the CREATE statement returned in the CLOB to set the length of the VARCHAR2 columns to a more appropriate value.

Also, note that the numbers in the partition name can vary.

Now that the table is created, executing a SELECT * statement returns all of the rows.  Note that the SET LINESIZE executed above means that SQL*Plus uses 132 character for customer_name and postal_code.

SQL> select * from customer_list_hive order by customer_number;

CUSTOMER_NUMBER
---------------
CUSTOMER_NAME
------------------------------------------------------------------------------------------------------------------------------POSTAL_CODE
------------------------------------------------------------------------------------------------------------------------------              1
 AAAAA Plumbing
01372

             13
 Andi's Doughnuts
01372

             28
 Sparkly Laundry
07101

             51
 DIY Supplies
07101

             87
 Fast Frames
01754

             89
 Friendly Pharmacy
01372

            105
 Le Bistrot du Chat Noir
01754

            121
 Pleasant Pets
01754

            130
 Bailey the Bookmonger
01754

            210
 The Electric Eel Diner
07101

            222
 Everyt'ing General Store
01372

            231
 Big Rocket Market
01754


12 rows selected.

SQL>

SQL execution uses the partition information to prune partitions that do not match the criteria in the WHERE clause.

SQL> select customer_number, customer_name, postal_code
  2    from customer_list_hive
  3    where postal_code = '01754'
  4    order by customer_number;

CUSTOMER_NUMBER
---------------
CUSTOMER_NAME
------------------------------------------------------------------------------------------------------------------------------POSTAL_CODE
------------------------------------------------------------------------------------------------------------------------------             87
 Fast Frames
01754

            105
 Le Bistrot du Chat Noir
01754

            121
 Pleasant Pets
01754

            130
 Bailey the Bookmonger
01754

            231
 Big Rocket Market
01754


5 rows selected.

SQL> 

Example 19-6 Using ORA_PARTITION_VALIDATION for Partition Testing

When you use the ORA_PARTITION_VALIDATION function, you can obtain a list of external table partition rows that are placed in the wrong partition. To demonstrate this feature, this example shows a partition created with the wrong department set followed by an example using the ORA_PARTITION_VALIDATION function to identify data in the incorrect partition:

create or replace directory def_dir1 as '/tmp';

REM create the exact same data in files locally
REM
set feedback 1
spool /tmp/xp1_15.txt
select '12#dept_12#xp1_15#' from dual;
spool off

spool /tmp/xp2_30.txt
select '29#dept_29#xp2_30#' from dual;
spool off

spool /tmp/xp2_wrong.txt
select '99#dept_99#xp2_wrong#' from dual;
spool off

drop table ept purge;
create table ept(deptno number,dname char(14),loc char(13))
organization external
( type oracle_loader
  default directory def_dir1
  access parameters(
    records delimited by newline
    fields terminated by '#')
)
reject limit unlimited
partition by range (deptno)
(
  partition ep1 values less than (10),
  partition ep2 values less than (20) location ('xp1_15.txt'),
  partition epwrong values less than (30) location ('xp2_wrong.txt')
)
;

select pt.*, ora_partition_validation(rowid) from pt;

Example 19-13 Loading Data From CSV Files With No Access Parameters

This example requires the following conditions:

• The order of the columns in the table must match the order of fields in the data file.

• The records in the data file must be terminated by newline.

• The field in the records in the data file must be separated by commas (if field values are enclosed in quotation marks, then the quotation marks are not removed from the field).

• There cannot be any newline characters in the middle of a field.

The data for the external table is as follows:

events_all.csv
Winter Games,10-JAN-2010,10,
Hockey Tournament,18-MAR-2009,3,
Baseball Expo,28-APR-2009,2,
International Football Meeting,2-MAY-2009,14,
Track and Field Finale,12-MAY-2010,3,
Mid-summer Swim Meet,5-JUL-2010,4,
Rugby Kickoff,28-SEP-2009,6,

The definition of the external table is as follows:

SQL> CREATE TABLE EVENTS_XT_1
  2  (EVENT       varchar2(30),
  3   START_DATE  date,
  4   LENGTH      number)
  5  ORGANIZATION EXTERNAL
  6  (default directory def_dir1 location ('events_all.csv'));

Table created.

The following shows a SELECT operation on the external table EVENTS_XT_1:

SQL> select START_DATE, EVENT, LENGTH
  2    from EVENTS_XT_1
  3    order by START_DATE;

START_DAT EVENT                              LENGTH
--------- ------------------------------ ----------
18-MAR-09 Hockey Tournament                       3
28-APR-09 Baseball Expo                           2
02-MAY-09 International Football Meeting         14
28-SEP-09 Rugby Kickoff                           6
10-JAN-10 Winter Games                           10
12-MAY-10 Track and Field Finale                  3
05-JUL-10 Mid-summer Swim Meet                    4

7 rows selected.

SQL> 

Example 19-14 Default Date Mask For the Session Does Not Match the Format of Data Fields in the Data File

This example is the same as the previous example, except that the default date mask for the session does not match the format of date fields in the data file.  In the example below, the session format for dates is DD-Mon-YYYY whereas the format of dates in the data file is MM/DD/YYYY. If the external table definition does not have a date mask, then the ORACLE_LOADER access driver uses the session date mask to attempt to convert the character data in the data file to a date data type. ou specify an access parameter for the date mask to use for all fields in the data file that are used to load date columns in the external table.

The following is the contents of the data file for the external table:

events_all_date_fmt.csv
Winter Games,1/10/2010,10
Hockey Tournament,3/18/2009,3
Baseball Expo,4/28/2009,2
International Football Meeting,5/2/2009,14
Track and Field Finale,5/12/2009,3
Mid-summer Swim Meet,7/5/2010,4
Rugby Kickoff,9/28/2009,6

The definition of the external table is as follows:

SQL> CREATE TABLE EVENTS_XT_2
  2  (EVENT       varchar2(30),
  3   START_DATE  date,
  4   LENGTH      number)
  5  ORGANIZATION EXTERNAL
  6  (default directory def_dir1
  7   access parameters (fields date_format date mask "mm/dd/yyyy")
  8   location ('events_all_date_fmt.csv'));

Table created.

SQL> 

The following shows a SELECT operation on the external table EVENTS_XT_2:

SQL> select START_DATE, EVENT, LENGTH
  2    from EVENTS_XT_2
  3    order by START_DATE;

START_DAT EVENT                              LENGTH
--------- ------------------------------ ----------
18-MAR-09 Hockey Tournament                       3
28-APR-09 Baseball Expo                           2
02-MAY-09 International Football Meeting         14
12-MAY-09 Track and Field Finale                  3
28-SEP-09 Rugby Kickoff                           6
10-JAN-10 Winter Games                           10
05-JUL-10 Mid-summer Swim Meet                    4

7 rows selected.

Example 19-15 Data is Split Across Two Data Files

This example is that same as the first example in this section except for the following:

• The data is split across two data files.

• Each data file has a row containing the names of the fields.

• Some fields in the data file are enclosed by quotation marks.

The FIELD NAMES ALL FILES tells the access driver that the first row in each file contains a row with names of the fields in the file. The access driver matches the names of the fields to the names of the columns in the table. This means the order of the fields in the file can be different than the order of the columns in the table. If a field name in the first row is not enclosed in quotation marks, then the access driver uppercases the name before trying to find the matching column name in the table. If the field name is enclosed in quotation marks, then it does not change the case of the names before looking for a matching name.

Because the fields are enclosed in quotation marks, the access parameter requires the CSV WITHOUT EMBEDDED RECORD TERMINATORS clause.  This clause states the following:

• Fields in the data file are separated by commas.

• If the fields are enclosed in double quotation marks, then the access driver removes them from the field value.

• There are no new lines embedded in the field values (this option allows the access driver to skip some checks that can slow the performance of SELECT operations on the external table).

The two data files are as follows:

events_1.csv

"EVENT","START DATE","LENGTH",
"Winter Games", "10-JAN-2010", "10"
"Hockey Tournament", "18-MAR-2009", "3"
"Baseball Expo", "28-APR-2009", "2"
"International Football Meeting", "2-MAY-2009", "14"

events_2.csv

Event,Start date,Length,
Track and Field Finale, 12-MAY-2009, 3
Mid-summer Swim Meet, 5-JUL-2010, 4
Rugby Kickoff, 28-SEP-2009, 6

The external table definition is as follows:

SQL> CREATE TABLE EVENTS_XT_3
  2  ("START DATE"  date,
  3   EVENT         varchar2(30),
  4   LENGTH        number)
  5  ORGANIZATION EXTERNAL
  6  (default directory def_dir1
  7   access parameters (records field names all files
  8                      fields csv without embedded record terminators)
  9   location ('events_1.csv', 'events_2.csv'));

Table created.

The following shows the result of a SELECT operation on the EVENTS_XT_3 external table:

SQL> select "START DATE", EVENT, LENGTH
  2    from EVENTS_XT_3
  3    order by "START DATE";

START DAT EVENT                              LENGTH
--------- ------------------------------ ----------
18-MAR-09 Hockey Tournament                       3
28-APR-09 Baseball Expo                           2
02-MAY-09 International Football Meeting         14
12-MAY-09 Track and Field Finale                  3
28-SEP-09 Rugby Kickoff                           6
10-JAN-10 Winter Games                           10
05-JUL-10 Mid-summer Swim Meet                    4

7 rows selected.

Example 19-16 Data Is Split Across Two Files and Only the First File Has a Row of Field Names

This example is the same as example 3 except that only the 1st file has a row of field names.  The first row of the second file has real data.  The RECORDS clause changes to "field names first file".

The two data files are as follows:

events_1.csv (same as for example 3)

"EVENT","START DATE","LENGTH",
"Winter Games", "10-JAN-2010", "10"
"Hockey Tournament", "18-MAR-2009", "3"
"Baseball Expo", "28-APR-2009", "2"
"International Football Meeting", "2-MAY-2009", "14"

events_2_no_header_row.csv

Track and Field Finale, 12-MAY-2009, 3
Mid-summer Swim Meet, 5-JUL-2010, 4
Rugby Kickoff, 28-SEP-2009, 6

The external table definition is as follows:

SQL> CREATE TABLE EVENTS_XT_4
  2  ("START DATE"  date,
  3   EVENT         varchar2(30),
  4   LENGTH        number)
  5  ORGANIZATION EXTERNAL
  6  (default directory def_dir1
  7   access parameters (records field names first file
  8                      fields csv without embedded record terminators)
  9   location ('events_1.csv', 'events_2_no_header_row.csv'));

Table created.

The following shows a SELECT operation on the EVENTS_XT_4 external table:

SQL> select "START DATE", EVENT, LENGTH
  2    from EVENTS_XT_4
  3    order by "START DATE";

START DAT EVENT                              LENGTH
--------- ------------------------------ ----------
18-MAR-09 Hockey Tournament                       3
28-APR-09 Baseball Expo                           2
02-MAY-09 International Football Meeting         14
12-MAY-09 Track and Field Finale                  3
28-SEP-09 Rugby Kickoff                           6
10-JAN-10 Winter Games                           10
05-JUL-10 Mid-summer Swim Meet                    4

7 rows selected.

Example 19-17 The Order of the Fields in the File Match the Order of the Columns in the Table

This example has the following conditions:

• The order of the fields in the file match the order of the columns in the table.

• Fields are separated by newlines and are optionally enclosed in double quotation marks.

• There are fields that have embedded newlines in their value and those fields are enclosed in double quotation marks.

The contents of the data files are as follows:

event_contacts_1.csv

Winter Games, 10-JAN-2010, Ana Davis,
Hockey Tournament, 18-MAR-2009, "Daniel Dube
Michel Gagnon",
Baseball Expo, 28-APR-2009, "Robert Brown"
Internation Football Meeting, 2-MAY-2009,"Pete Perez
Randall Barnes
Melissa Gray",

event_contacts_2.csv

Track and Field Finale, 12-MAY-2009, John Taylor,
Mid-summer Swim Meet, 5-JUL-2010, "Louise Stewart
Cindy Sanders"
Rugby Kickoff, 28-SEP-2009, "Don Nguyen
Ray Lavoie"

The table definition is as follows. The CSV WITH EMBEDDED RECORD TERMINATORS clause tells the access driver how to handle fields enclosed by double quotation marks that also have embedded new lines.

SQL> CREATE TABLE EVENTS_CONTACTS_1
  2  (EVENT       varchar2(30),
  3   START_DATE  date,
  4   CONTACT     varchar2(120))
  5  ORGANIZATION EXTERNAL
  6  (default directory def_dir1
  7   access parameters (fields CSV with embedded record terminators)
  8   location ('event_contacts_1.csv', 'event_contacts_2.csv'));

Table created.

The following shows the result of a SELECT operation on the EVENT_CONTACTS_1 external table:

SQL> column contact format a30 
SQL> select START_DATE, EVENT, CONTACT
  2    from EVENTS_CONTACTS_1
  3    order by START_DATE;

START_DAT EVENT                          CONTACT
--------- ------------------------------ ------------------------------
18-MAR-09 Hockey Tournament              Daniel Dube
                                         Michel Gagnon

28-APR-09 Baseball Expo                  Robert Brown
02-MAY-09 Internation Football Meeting   Pete Perez
                                         Randall Barnes
                                         Melissa Gray

12-MAY-09 Track and Field Finale         John Taylor
28-SEP-09 Rugby Kickoff                  Don Nguyen
                                         Ray Lavoie

10-JAN-10 Winter Games                   Ana Davis
05-JUL-10 Mid-summer Swim Meet           Louise Stewart
                                         Cindy Sanders

7 rows selected.

Example 19-18 Not All Fields in the Data File Use Default Settings for the Access Parameters

This example shows what to do when most field in the data file use default settings for the access parameters but a few do not.  Instead of listing the setting for all fields, this example shows how you can set attributes for just the fields that are different from the default. The differences are as follows:

• there are two date fields, one of which uses the session format, but registration_deadline  uses a different format

• registration_deadline also uses a value of NONE to indicate a null value.

The content of the data file is as follows:

events_reg.csv

Winter Games,10-JAN-2010,10,12/1/2009,
Hockey Tournament,18-MAR-2009,3,3/11/2009,
Baseball Expo,28-APR-2009,2,NONE
International Football Meeting,2-MAY-2009,14,3/1/2009
Track and Field Finale,12-MAY-2010,3,5/10/010
Mid-summer Swim Meet,5-JUL-2010,4,6/20/2010
Rugby Kickoff,28-SEP-2009,6,NONE  

The table definition is as follows. The ALL FIELDS OVERRIDE clause allows you to specify information for that field while using defaults for the remaining fields. The remaining fields have a data type of CHAR(255) and the field data is terminated by a comma with a trimming option of LDRTRIM.

SQL> CREATE TABLE EVENT_REGISTRATION_1
  2  (EVENT                 varchar2(30),
  3   START_DATE            date,
  4   LENGTH                number,
  5   REGISTRATION_DEADLINE date)
  6  ORGANIZATION EXTERNAL
  7  (default directory def_dir1
  8   access parameters
  9  (fields all fields override
 10     (REGISTRATION_DEADLINE CHAR (10) DATE_FORMAT DATE MASK "mm/dd/yyyy"
 11                           NULLIF REGISTRATION_DEADLINE = 'NONE'))
 12   location ('events_reg.csv'));

Table created.

The following shows the result of a SELECT operation on the EVENT_REGISTRATION_1 external table:

SQL> select START_DATE, EVENT, LENGTH, REGISTRATION_DEADLINE
  2    from EVENT_REGISTRATION_1
  3    order by START_DATE;

START_DAT EVENT                              LENGTH REGISTRAT
--------- ------------------------------ ---------- ---------
18-MAR-09 Hockey Tournament                       3 11-MAR-09
28-APR-09 Baseball Expo                           2
02-MAY-09 International Football Meeting         14 01-MAR-09
28-SEP-09 Rugby Kickoff                           6
10-JAN-10 Winter Games                           10 01-DEC-09
12-MAY-10 Track and Field Finale                  3 10-MAY-10
05-JUL-10 Mid-summer Swim Meet                    4 20-JUN-10

7 rows selected.