Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

CHAPTER 10 ■ DATABASE TABLES 353
That aside, what is important to know about heap tables? Well, the CREATE TABLE syntax
spans some 72 pages in the Oracle SQL Reference manual, so there are lots of options that go
along with them. There are so many options that getting a hold on all of them is pretty difficult.
The “wire diagrams” (or “train track” diagrams) alone take 18 pages to cover. One trick I
use to see most of the options available to me in the CREATE TABLE statement for a given table
is to create the table as simply as possible, for example:
ops$tkyte@ORA10GR1> create table t
2 ( x int primary key,
3 y date,
4 z clob
5 )
6 /
Table created.
Then, using the standard supplied package DBMS_METADATA, I query the definition of it and
see the verbose syntax:
ops$tkyte@ORA10GR1> select dbms_metadata.get_ddl( 'TABLE', 'T' ) from dual;
DBMS_METADATA.GET_DDL('TABLE','T')
-------------------------------------------------------------------------------
CREATE TABLE "OPS$TKYTE"."T"
( "X" NUMBER(*,0),
"Y" DATE,
"Z" CLOB,
PRIMARY KEY ("X")
USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
TABLESPACE "USERS" ENABLE
) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
TABLESPACE "USERS"
LOB ("Z") STORE AS (
TABLESPACE "USERS" ENABLE STORAGE IN ROW CHUNK 8192 PCTVERSION 10
NOCACHE
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT))
The nice thing about this trick is that it shows many of the options for my CREATE TABLE
statement. I just have to pick data types and such, and Oracle will produce the verbose version
for me. I can now customize this verbose version, perhaps changing the ENABLE STORAGE IN ROW
to DISABLE STORAGE IN ROW, which would disable the storage of the LOB data in the row with the
structured data, causing it to be stored in another segment. I use this trick all of the time to
save the couple minutes of confusion I would otherwise have if I were trying to figure this all
out from the huge wire diagrams. I can also use this technique to learn what options are available
to me on the CREATE TABLE statement under different circumstances.