1) Yes, a) is a heap table I know that, but b) is a heap table? Yes, b) is a Heap Table PLUS an Index - the Table and Index are separate objects. 2) Is there any advantage of bumping up the C1 column to PK, like storage, performance? It depends. Does C1 not have a Unique Index definition yet ? You probably need to cleanup duplicates first. There is no storage benefit with a PK. A PK, in itself, doesn't offer a performance benefit if there's already an index. A PK is more about "clean" data and proper design. 3) Is b) and c) are the same? No. b) has a heap table and a separate index. c) is an IOT. 4) Say my application is already out in the customers site, changing the C1 to PK would be tricky, instead can do solution d) ? I wouldn't advise it. Hemant K Chitale From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Nik Tek Sent: Wednesday, April 02, 2014 7:21 AM To: oracle-l@xxxxxxxxxxxxx Subject: Is table with b-tree index is still a heap table? Hi, I have question about oracle heap tables vs. tables with b-tree index vs. IOT tables. Say I have a table T1 a) CREATE TABLE T1 (C1 NUMBER NOT NULL, C2 VARCHAR2(100)); b) CREATE TABLE T1 (C1 NUMBER NOT NULL, C2 VARCHAR2(100)); CREATE INDEX IDX_T1_C1 ON T1(C1); c) CREATE TABLE T1 (C1 NUMBER NOT NULL, C2 VARCHAR2(100), CONSTRAINT PK_T1_C1 PRIMARY KEY (C1) ORGANIZATION INDEX); d) CREATE SEQUENCE T1_SEQ INCREMENT BY 1; / ALTER TABLE T1 ADD SURR_KEY INTEGER NOT NULL; / ALTER TABLE T1 ADD CONSTRAINT PK_T1_C1_SK PRIMARY KEY (C1,SURR_KEY); / CREATE OR REPLACE TRIGGER T1_TRIG BEFORE INSERT ON T1 FOR EACH ROW BEGIN SELECT T1_SEQ.nextval INTO :NEW.SURR_KEY FROM dual; END; Questions: 1) Yes, a) is a heap table I know that, but b) is a heap table? 2) Is there any advantage of bumping up the C1 column to PK, like storage, performance? 3) Is b) and c) are the same? 4) Say my application is already out in the customers site, changing the C1 to PK would be tricky, instead can do solution d) ? Thank you Nik This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at https://www.sc.com/en/incorporation-details.html.