1. 11 Copyright © Oracle Corporation, 2001. All rights reserved. Managing Tables

2. 11-2 Copyright © Oracle Corporation, 2001. All rights reserved. Objectives After completing this lesson, you should be able to do the following: Identify the various methods of storing data Outline Oracle data types Distinguish between an extended versus a restricted ROWID Outline the structure of a row Create regular and temporary tables Manage storage structures within a table Reorganize, truncate, drop a table Drop a column within a table

3. 11-3 Copyright © Oracle Corporation, 2001. All rights reserved. Storing User Data Regular table Cluster Partitioned table Index-organized table

4. 11-4 Copyright © Oracle Corporation, 2001. All rights reserved.

5. 11-5 Copyright © Oracle Corporation, 2001. All rights reserved.

6. 11-6 Copyright © Oracle Corporation, 2001. All rights reserved. Oracle Built-in Data Types CHAR(N), NCHAR(N) VARCHAR2(N), NVARCHAR2(N) NUMBER(P,S) DATE TIMESTAMP RAW(N) BLOB, CLOB, NCLOB, BFILE LONG, LONG RAW ROWID, UROWID VARRAY TABLE REF Data type Built-in User-defined ScalarRelationshipCollection

7. 11-7 Copyright © Oracle Corporation, 2001. All rights reserved.

8. 11-8 Copyright © Oracle Corporation, 2001. All rights reserved.

9. 11-9 Copyright © Oracle Corporation, 2001. All rights reserved.

10. 11-10 Copyright © Oracle Corporation, 2001. All rights reserved. ROWID Format Extended ROWID Format Restricted ROWID Format OOOOOOBBBBBBFFFRRR Data object number Relative file number Row numberBlock number BBBBBBBBFFFFRRRR Block numberRow numberFile number..

11. 11-11 Copyright © Oracle Corporation, 2001. All rights reserved.

12. 11-12 Copyright © Oracle Corporation, 2001. All rights reserved. Structure of a Row Database block Row header Column length Column value

13. 11-13 Copyright © Oracle Corporation, 2001. All rights reserved. Creating a Table CREATE TABLE hr.employees( employee_id NUMBER(6), first_nameVARCHAR2(20), last_name VARCHAR2(25), email VARCHAR2(25), phone_number VARCHAR2(20), hire_date DATE DEFAULT SYSDATE, job_id VARCHAR2(10), salary NUMBER(8,2), commission_pct NUMBER (2,2), manager_id NUMBER(6), department_id NUMBER(4) );

14. 11-14 Copyright © Oracle Corporation, 2001. All rights reserved.

15. 11-15 Copyright © Oracle Corporation, 2001. All rights reserved.

16. 11-16 Copyright © Oracle Corporation, 2001. All rights reserved.

17. 11-17 Copyright © Oracle Corporation, 2001. All rights reserved. Creating a Table: Guidelines Place tables in separate tablespaces. Use locally-managed tablespaces to avoid fragmentation. Use few standard extent sizes for tables to reduce tablespace fragmentation.

18. 11-18 Copyright © Oracle Corporation, 2001. All rights reserved. Creating Temporary Tables Created using the GLOBAL TEMPORARY clause Tables retain data only for the duration of a transaction or session DML locks are not acquired on the data Can create indexes, views, and triggers on temporary tables CREATE GLOBAL TEMPORARY TABLE hr.employees_temp AS SELECT * FROM hr.employees;

19. 11-19 Copyright © Oracle Corporation, 2001. All rights reserved. (Average Row Size - Initial Row Size) * 100 Average Row Size -- Average Row Size * 100 100 - PCTFREE - Available Data Space Setting PCTFREE and PCTUSED Compute PCTFREE Compute PCTUSED

20. 11-20 Copyright © Oracle Corporation, 2001. All rights reserved. Before updateAfter update Pointer Row Migration and Chaining

21. 11-21 Copyright © Oracle Corporation, 2001. All rights reserved. Changing Storage and Block Utilization Parameters ALTER TABLE hr.employees PCTFREE 30 PCTUSED 50 STORAGE(NEXT 500K MINEXTENTS 2 MAXEXTENTS 100);

22. 11-22 Copyright © Oracle Corporation, 2001. All rights reserved.

23. 11-23 Copyright © Oracle Corporation, 2001. All rights reserved.

24. 11-24 Copyright © Oracle Corporation, 2001. All rights reserved. Manually Allocating Extents ALTER TABLE hr.employees ALLOCATE EXTENT(SIZE 500K DATAFILE /DISK3/DATA01.DBF);

25. 11-25 Copyright © Oracle Corporation, 2001. All rights reserved. Nonpartitioned Table Reorganization When a nonpartitioned table is reorganized, its structure is kept, but not its contents. Used to move a table to a different tablespace or reorganize extents. ALTER TABLE hr.employees MOVE TABLESPACE data1;

26. 11-26 Copyright © Oracle Corporation, 2001. All rights reserved. Truncating a Table Truncating a table deletes all rows in a table and releases used space. Corresponding indexes are truncated. TRUNCATE TABLE hr.employees;

27. 11-27 Copyright © Oracle Corporation, 2001. All rights reserved. Dropping a Table DROP TABLE hr.department CASCADE CONSTRAINTS;

28. 11-28 Copyright © Oracle Corporation, 2001. All rights reserved.

29. 11-29 Copyright © Oracle Corporation, 2001. All rights reserved. Dropping a Column Removing a column from a table: Removes the column length and data from each row, freeing space in the data block. Dropping a column in a large table takes a considerable amount of time. ALTER TABLE hr.employees DROP COLUMN comments CASCADE CONSTRAINTS CHECKPOINT 1000;

30. 11-30 Copyright © Oracle Corporation, 2001. All rights reserved.

31. 11-31 Copyright © Oracle Corporation, 2001. All rights reserved. Using the UNUSED Option Mark a column as unused: Drop unused columns: Continue to drop column operation: ALTER TABLE hr.employees SET UNUSED COLUMN comments CASCADE CONSTRAINTS; ALTER TABLE hr.employees DROP UNUSED COLUMNS CHECKPOINT 1000; ALTER TABLE hr.employees DROP COLUMNS CONTINUE CHECKPOINT 1000;

32. 11-32 Copyright © Oracle Corporation, 2001. All rights reserved.

33. 11-33 Copyright © Oracle Corporation, 2001. All rights reserved. Obtaining Table Information Information about tables can be obtained by querying the following views: DBA_TABLES DBA_OBJECTS

34. 11-34 Copyright © Oracle Corporation, 2001. All rights reserved.

35. 11-35 Copyright © Oracle Corporation, 2001. All rights reserved. Summary In this lesson, you should have learned how to: Distinguish between an extended versus a restricted ROWID Outline the structure of a row Create regular and temporary tables Manage storage structures within a table Reorganize, truncate, and drop a table Drop a column within a table

36. 11-36 Copyright © Oracle Corporation, 2001. All rights reserved. Practice 11 Overview This practice covers the following topics: Creating a table Viewing, marking as unused, and dropping columns within a table Allocating extents manually Truncating a table Obtaining table information

37. 11-37 Copyright © Oracle Corporation, 2001. All rights reserved.

38. 11-38 Copyright © Oracle Corporation, 2001. All rights reserved.