1. Using Clusters and Index-Organized Tables

2. Objectives Creating and maintaining clusters
Using index-organized tables
Retrieving information about clusters and tables from the data dictionary

3. Distribution of Rows Within a Table
Cluster
Index-organized table
Ordering of Rows
Random
Grouped
Ordered

4. Clusters Unclustered ORD and ITEM tables Clustered ORD and ITEM tables
ORD_NO PROD QTY
101 A
102 A
102 G
102 N
101 A
101 W
ORD_NO ORD_DT CUST_CD
JAN R01
JAN N45
Cluster Key
(ORD_NO)
101 ORD_DT CUST_CD
05-JAN-97 R01
PROD QTY A A W
ORD_DT CUST_CD
07-JAN-97 N45 A G N
Unclustered ORD and ITEM tables
Clustered ORD and ITEM tables

5. Cluster Types
Index cluster
Hash cluster
Hash function

6. Creating Index Clusters
. Create a cluster.
. Create a cluster index.
CREATE CLUSTER scott.ord_clu (ord_no NUMBER(3)) SIZE 200 TABLESPACE DATA01 STORAGE(INITIAL 5M NEXT 5M PCTINCREASE 0);
CREATE INDEX scott.ord_clu_idx
ON CLUSTER scott.ord_clu
TABLESPACE INDX01 STORAGE(INITIAL 1M NEXT 1M PCTINCREASE 0);

7. Creating Index Clusters
. Create tables in the cluster.
CREATE TABLE scott.ord
(ord_no NUMBER(3) CONSTRAINT ord_pk PRIMARY KEY, ord_dt DATE, cust_cd VARCHAR2(3)) CLUSTER scott.ord_clu(ord_no);
CREATE TABLE scott.item
(ord_no NUMBER(3) CONSTRAINT item_ord_fk REFERENCES scott.ord, prod VARCHAR2(5), qty NUMBER(3), CONSTRAINT item_pk PRIMARY KEY(ord_no,prod)) CLUSTER scott.ord_clu(ord_no);

8. Creating Hash Clusters
. Create a cluster.
. Create tables in a cluster.
CREATE CLUSTER scott.off_clu (country VARCHAR2(2),postcode VARCHAR2(8)) SIZE 500 HASHKEYS 1000
TABLESPACE DATA01 STORAGE(INITIAL 5M NEXT 5M PCTINCREASE 0);
CREATE TABLE scott.office( office_cd NUMBER(3), cost_ctr NUMBER(3), country VARCHAR2(2), postcode VARCHAR2(8)) CLUSTER scott.off_clu(country,postcode);

9. Parameters Specific to Hash Clusters
HASHKEYS: Number of key values
HASH IS: Optional user-defined hash function
Key 21
Key 12
Key 11
Key 1
Key 2
Key 3
Key 22
Overflow block
Preallocated blocks

10. Dropping Clusters Use INCLUDING TABLES to drop tables and cluster
or drop tables before dropping cluster.
DROP CLUSTER scott.ord_clu
INCLUDING TABLES;
DROP TABLE scott.ord;
DROP TABLE scott.item;
DROP CLUSTER scott.ord_clu;

11. Index-Organized Tables
Indexed access on table
Accessing index- organized table
ROWID
Non-key columns
Key column
Row header

12. Creating Index-Organized Tables
CREATE TABLE scott.sales ( office_cd NUMBER(3), qtr_end DATE,
revenue NUMBER(10,2),
review VARCHAR2(1000), CONSTRAINT sales_pk PRIMARY KEY(office_code, qtr_end))
ORGANIZATION INDEX TABLESPACE data01
PCTTHRESHOLD 20
OVERFLOW TABLESPACE data02;

13. Summary Identifying situations where clusters are useful
Using index-organized tables