External table Enhancements in Oracle 12c

One of the External tables’ enhancements in Oracle 12c is the ability to use wildcard characters in defining the data sources. We can have either ? ( to denote single character substitution ) or * ( multiple character substitution ) in denoting the location of the data files .

Here is an simple example .

Let us create few CSV files.

C:\extdir>dir

Volume in drive C has no label.
Volume Serial Number is 8280–8864
Directory of C:\extdir
07/06/2015 01:45 PM .
07/06/2015 01:45 PM ..
07/06/2015 01:37 PM 27 emp1.txt
07/06/2015 01:38 PM 26 emp2.txt
07/06/2015 01:44 PM 52 emp500.txt
3 File(s) 105 bytes
2 Dir(s) 168,809,664,512 bytes free

C:\extdir>type emp1.txt
101,zahir,F
102,mohamed,R

C:\extdir>type emp2.txt

201,Hameed,A
252,Abdul,R

C:\extdir>type emp500.txt
511,Balasubramaniam,A
577,Yesudas,A
501,Janaki,A

Let us create an external table with Single character in the wild card.

CREATE TABLE EMP_EXT
(
"EMP_ID" VARCHAR2(1000 BYTE),
"EMP_NAME" VARCHAR2(1000 BYTE),
"EMP_TYPE" VARCHAR2(1000 BYTE)
)
ORGANIZATION EXTERNAL
(
TYPE ORACLE_LOADER DEFAULT DIRECTORY "EX_TAB_DIR"
ACCESS PARAMETERS
( debug = 3
RECORDS DELIMITED BY NEWLINE
CHARACTERSET we8mswin1252
BADFILE EX_TAB_DIR:'emp_ext.bad_xt'
LOGFILE 'emp_ext.log_xt'
FIELDS TERMINATED BY ","
LDRTRIM MISSING FIELD VALUES ARE NULL
REJECT ROWS WITH ALL NULL FIELDS
) LOCATION ( 'emp?.txt')
)
REJECT LIMIT UNLIMITED ;

SQL> Select * from emp_ext ;

EMP_I EMP_NAME EMP_T
 - - - - - - - - - - - - - - - - - - -
101 zahir F
102 mohamed R
201 Hameed A
252 Abdul R

As we have given ‘?’ in the wildcard , the external table created above did not take in the records from emp500.txt.

Let us create another table with ‘*’ in the wildcard as below.

CREATE TABLE EMP_EXT_MULTI
(
"EMP_ID" VARCHAR2(1000 BYTE),
"EMP_NAME" VARCHAR2(1000 BYTE),
"EMP_TYPE" VARCHAR2(1000 BYTE)
)
ORGANIZATION EXTERNAL
(
TYPE ORACLE_LOADER DEFAULT DIRECTORY "EX_TAB_DIR"
ACCESS PARAMETERS
( debug = 3
RECORDS DELIMITED BY NEWLINE
CHARACTERSET we8mswin1252
BADFILE EX_TAB_DIR:'emp_m_ext.bad_xt'
LOGFILE 'emp_m_ext.log_xt'
FIELDS TERMINATED BY ","
LDRTRIM MISSING FIELD VALUES ARE NULL
REJECT ROWS WITH ALL NULL FIELDS
) LOCATION ( 'emp*.txt')
)
REJECT LIMIT UNLIMITED ;

SQL> Select * from EMP_EXT_MULTI ;

EMP_I EMP_NAME EMP_T
 - - - - - - - - - - - - - - - - - - -
101 zahir F
102 mohamed R
201 Hameed A
252 Abdul R
511 Balasubramaniam A
577 Yesudas A
501 Janaki A

As can be seen from the above example , the external table did bring in the contents of all files starting with the filenames ‘emp…..txt’.

Originally published at https://zahirmohideen.blogspot.com/2015/07/external-table-enhancements-in-oracle.html