1. Dr. Chen, Oracle Database System (Oracle) 1 Chapter 6 Additional Database Objects (up to p.195 and all in the pptx file) Jason C. H. Chen, Ph.D. Professor of MIS School of Business Gonzaga University Spokane, WA 99258 USA chen@jepson.gonzaga.edu

2. Dr. Chen, Oracle Database System (Oracle) 2 Objectives Define the purpose of a sequence and state how it can be used in a database Explain why gaps may appear in the integers generated by a sequence Use the CREATE SEQUENCE command to create a sequence Call and use sequence values Identify which options cannot be changed by the ALTER SEQUENCE command Delete a sequence Create indexes with the CREATE INDEX command Explain the main index structures: B-tree and bitmap

3. Dr. Chen, Oracle Database System (Oracle) 3 Objectives (continued) Verify index use with the explain plan Introduce variations on conventional indexes, including a function-based index and an index organized table Verify index existence via the data dictionary Rename an index with the ALTER INDEX command Remove an index using the DROP INDEX command Create and remove a public synonym

4. Dr. Chen, Oracle Database System (Oracle) 4 Database Objects An object is anything that has a name and defined structure Includes: –Table – stores data –Sequence – generates sequential integers –Index – allows users to quickly locate specific records –Synonym – alias for other database objects

5. Dr. Chen, Oracle Database System (Oracle) 5 Sequences Used for internal control purposes by providing sequential integers for auditing Used to generate unique value for primary key column –Surrogate key = no correlation with actual row contents

6. Dr. Chen, Oracle Database System (Oracle) 6 Creating a Sequence Use the CREATE SEQUENCE command Various intervals are allowed – Default: 1 You can specify the starting number – Default: 1 CREATE SEQUENCE sequencename [INCREASE BY value] [START WITH value] [{MAXVALUE value | MAXVALUE}] [{MINVALUE value | MINVALUE}] [{CYCLE | NOCYLE}] [{ORDER | NOORDER}] [{CACHE value | NOCACHE}]; Figure 6-1 Syntax of the CREATE SEQUENCE command

7. Dr. Chen, Oracle Database System (Oracle) 7 Creating a Sequence (continued) Can specify MINVALUE for decreasing sequence and MAXVALUE for increasing sequence Numbers can be reused if CYCLE is specified –The options determine whether Oracle should begin reissuing values from the sequence after reaching the minimum or maximum value. ORDER clause is used in application cluster environment Use CACHE to pregenerate integers – Default: 20

8. Dr. Chen, Oracle Database System (Oracle) 8 ORDERS Data Files

9. Dr. Chen, Oracle Database System (Oracle) 9 Refresh the Database 1. Go to Blackboard and download (two) data files from Oracle chapter6 and save under c:\oradata\chapter6\ 2. Run the following script file –Start c:\oradata\chapter6\JLDB_Build_6.sql

10. Dr. Chen, Oracle Database System (Oracle) 10 Creating a Sequence (continued) Figure 6-3 Syntax of the INSERT command

11. Dr. Chen, Oracle Database System (Oracle) 11 Creating a Sequence (continued) Figure 6-4 Query USER-OBJECTS to verify existing sequence

12. Dr. Chen, Oracle Database System (Oracle) 12 Creating a Sequence (continued) To verify the settings for options of a sequence, query USER_SEQUENCES data dictionary view Next Number to issue Figure 6-5 Verifying sequence option settings SELECT SEQUENCE_NAME FROM USER_SEQUENCES; SEQUENCE_NAME ------------------------------ ORDERS_ORDER#_SEQ

13. Dr. Chen, Oracle Database System (Oracle) 13 Using Sequence Values NEXTVAL – generates integer Figure 6-6 Inserting a row, using a sequence to provide a PRIMARY KEY value

14. Dr. Chen, Oracle Database System (Oracle) 14 Using Sequence Values (continued) Figure 6-7 Order added, using a sequence value for the Order#

15. Dr. Chen, Oracle Database System (Oracle) 15 Using Sequence Values (continued) CURRVAL – contains last integer generated by NEXTVAL Figure 6-8 Using CURRVAL to insert an order detail row cpk INSERT INTO orderitems (order#, item#, isbn, quantity, paideach) VALUES (orders_order#_seq.CURRVAL, 1, 8117949391, 1, 8.50);

16. Dr. Chen, Oracle Database System (Oracle) 16 Using Sequence Values (continued) Figure 6-9 Verify the CURRVAL value

17. Dr. Chen, Oracle Database System (Oracle) 17 Altering Sequence Definitions Use ALTER SEQUENCE command to change the settings for a sequence START WITH value cannot be altered – drop the sequence and re-create it Changes cannot make current integers invalid

18. Dr. Chen, Oracle Database System (Oracle) 18 ALTER SEQUENCE Command Example Figure 6-11 Command to change the INCREMENT BY setting for a sequence

19. Dr. Chen, Oracle Database System (Oracle) 19 Checking Values on Sequences and SYSDATE Figure 6-12 New setting for the ORDERS_ORDER#_SEQ sequence Figure 6-13 Using the DUAL table

20. Dr. Chen, Oracle Database System (Oracle) 20 Checking Values on Sequences Figure 6-14 Testing sequence values with the DUAL table Why 1041?

21. Dr. Chen, Oracle Database System (Oracle) 21 Removing a Sequence Use the DROP SEQUENCE command to delete a sequence Previous values generated are not affected by removing a sequence from a database Figure 6-16 Dropping the ORDERS_ORDER#_SEQ sequence

22. Dr. Chen, Oracle Database System (Oracle) 22 Removing a Sequence (continued) Figure 6-17 Verify that the sequence is removed

23. Dr. Chen, Oracle Database System (Oracle) 23 Indexes – Query Optimization If database query activity (e.g., process speed) is the priority –Indexes should be considered If database operations involve more DML actions than query actions –Index creation should be minimized An index stores frequently referenced values and ROWIDs Can be based on one column, multiple columns, functions, or expressions

24. Dr. Chen, Oracle Database System (Oracle) 24 B-Tree Index Figure 6-19 B-tree index organization

25. Dr. Chen, Oracle Database System (Oracle) 25 B-Tree Index (continued) Implicitly create an index by PRIMARY KEY and UNIQUE constraints Explicitly create an index by using the CREATE INDEX command For example: SELECT index_name FROM user_indexes; -- result on the next slide

26. Dr. Chen, Oracle Database System (Oracle) 26 Examples on Query Optimization Note that the following slides are not in the text. Please study them thoroughly and practice all examples (SQL commands are available in the ‘Ch6Queries.sql’.

27. Dr. Chen, Oracle Database System (Oracle) 27 INDEX_NAME ------------------------------ ACCTBONUS_AMID_PK BOOKAUTHOR_PK ORDERITEMS_PK BOOKS_ISBN_PK BOOKS_COST_IDX AUTHOR_AUTHORID_PK PUBLISHER_PUBID_PK ORDERS_ORDER#_PK CUSTOMERS_ZIP_DESC_IDX CUSTOMERS_ZIP_IDX CUSTOMERS_CUSTOMER#_PK EMPLOYEES_EMPNO_PK PT_CHARG_PATIENTNO_ITEMCODE_PK ITEM_ITEM_CODE_PK ROOM_ROOM_NO_PK ACCOMODATION_ACCOM_ID_PK DOCTOR_PHYSCIAN_ID__PK PATIENT_PATIENT_NO_PK LOCATION_LOC_ID_PK INDEX_NAME ------------------------------ ENROLLMENT_PK COURSE_SECTION_CSEC_ID_PK COURSE_COURSE_ID_PK TERM_TERM_ID_PK STUDENT_S_ID_PK SYS_IL0000110103C00010$$ FACULTY_F_ID_PK PUBLISHER3_PUBID_PK PUBLISHER2_PUBID_PK REPCONTRACTS_PK BOOKSTORES_ID_PK BOOKSTORES_NAME_UK STOREREPS_ID_PK 32 rows selected. For example: SELECT index_name FROM user_indexes; What specific information is displayed on the output? Answer: _____ Since they are all implicitly indexed.

28. Dr. Chen, Oracle Database System (Oracle) 28 Implicitly Index (cont.) -- enter in SQL DEVELOPER SELECT table_name, index_name, index_type FROM user_indexes;

29. Dr. Chen, Oracle Database System (Oracle) 29 Optimizing Query Processing - A Quick Way to Speed Access to Your data Indexes may be used to improve the efficiency of data searches to meet particular search criteria after the table has been in use for some time. Therefore, the ability to create indexes quickly and efficiently at any time is important. SQL indexes can be created on the basis of any selected attributes

30. Dr. Chen, Oracle Database System (Oracle) 30 BOOKS ISBNTitlePubDatePubIDCostRetailDiscountCategory VARCHAR2(10)VARCHAR2(30)DATENUMBER(2)NUMBER(5,2) NUMBER(4,2)VARCHAR2(12) BOOKS Optimizing Query Processing – an example (not in the text)

31. Dr. Chen, Oracle Database System (Oracle) 31 -- chapter 6, (about the same as Figure 6-30; p. 199 ) -- 'BOOKS' must be in upper case SELECT table_name, index_name, index_type FROM user_indexes WHERE table_name = 'BOOKS'; ISBN TITLE COST CATEGORY ---------- ------------------------------ ---------- ------------ 4981341710 BUILDING A CAR WITH TOOTHPICKS 37.8 CHILDREN 8843172113 DATABASE IMPLEMENTATION 31.4 COMPUTER 3957136468 HOLY GRAIL OF ORACLE 47.25 COMPUTER 1915762492 HANDCRANKED COMPUTERS 21.8 COMPUTER 9959789321 E-BUSINESS THE EASY WAY 37.9 COMPUTER 2491748320 PAINLESS CHILD-REARING 48 FAMILY LIFE 2147428890 SHORTEST POEMS 21.85 LITERATURE 7 rows selected. SELECT isbn, title, cost, category FROM books WHERE cost > 20; Optimizing Query Processing

32. Dr. Chen, Oracle Database System (Oracle) 32 Optimizing Query Processing (conti.) Syntax: CREATE INDEX name_of_index ON table_name (field_to_be_indexed); For example (but, do not enter the SQL command now): CREATE INDEX books_cost_idx ON books (cost); Note that this statement defines an index called books_cost_idx for the cost column in the books table. This index ensures that in the next example SQL only needs to look at row in the database that satisfy the WHERE condition, and is, therefore, quicker to produce an answer.

33. Dr. Chen, Oracle Database System (Oracle) 33 Optimizing Query Processing (conti.) Type the following SQL: SELECT isbn, title, cost, category FROM books WHERE cost > 20; ISBN TITLE COST CATEGORY ---------- ------------------------------ ---------- ------------ 4981341710 BUILDING A CAR WITH TOOTHPICKS 37.8 CHILDREN 8843172113 DATABASE IMPLEMENTATION 31.4 COMPUTER 3957136468 HOLY GRAIL OF ORACLE 47.25 COMPUTER 1915762492 HANDCRANKED COMPUTERS 21.8 COMPUTER 9959789321 E-BUSINESS THE EASY WAY 37.9 COMPUTER 2491748320 PAINLESS CHILD-REARING 48 FAMILY LIFE 2147428890 SHORTEST POEMS 21.85 LITERATURE 7 rows selected. CREATE INDEX books_cost_idx ON books (cost); SQL> CREATE INDEX books_cost_idx ON books (cost); Index created.

34. Dr. Chen, Oracle Database System (Oracle) 34 Optimizing Query Processing (conti.) SELECT isbn, title, cost, category FROM books WHERE cost > 20; ISBN TITLE COST CATEGORY ---------- ------------------------------ ---------- ------------ 1915762492 HANDCRANKED COMPUTERS 21.8 COMPUTER 2147428890 SHORTEST POEMS 21.85 LITERATURE 8843172113 DATABASE IMPLEMENTATION 31.4 COMPUTER 4981341710 BUILDING A CAR WITH TOOTHPICKS 37.8 CHILDREN 9959789321 E-BUSINESS THE EASY WAY 37.9 COMPUTER 3957136468 HOLY GRAIL OF ORACLE 47.25 COMPUTER 2491748320 PAINLESS CHILD-REARING 48 FAMILY LIFE 7 rows selected. What is the difference on the output between these two versions?

35. Dr. Chen, Oracle Database System (Oracle) 35 Before “INDEX”. ISBN TITLE COST CATEGORY ---------- ------------------------------ ---------- ------------ 4981341710 BUILDING A CAR WITH TOOTHPICKS 37.8 CHILDREN 8843172113 DATABASE IMPLEMENTATION 31.4 COMPUTER 3957136468 HOLY GRAIL OF ORACLE 47.25 COMPUTER 1915762492 HANDCRANKED COMPUTERS 21.8 COMPUTER 9959789321 E-BUSINESS THE EASY WAY 37.9 COMPUTER 2491748320 PAINLESS CHILD-REARING 48 FAMILY LIFE 2147428890 SHORTEST POEMS 21.85 LITERATURE 7 rows selected. After “INDEX”. ISBN TITLE COST CATEGORY ---------- ------------------------------ ---------- ------------ 1915762492 HANDCRANKED COMPUTERS 21.8 COMPUTER 2147428890 SHORTEST POEMS 21.85 LITERATURE 8843172113 DATABASE IMPLEMENTATION 31.4 COMPUTER 4981341710 BUILDING A CAR WITH TOOTHPICKS 37.8 CHILDREN 9959789321 E-BUSINESS THE EASY WAY 37.9 COMPUTER 3957136468 HOLY GRAIL OF ORACLE 47.25 COMPUTER 2491748320 PAINLESS CHILD-REARING 48 FAMILY LIFE 7 rows selected.

36. Dr. Chen, Oracle Database System (Oracle) 36 SELECT table_name, index_name, index_type FROM user_indexes WHERE table_name = 'BOOKS'; Index on Query Optimization

37. Dr. Chen, Oracle Database System (Oracle) 37 Index on Query Optimization (conti.) -- default is ‘ASCENDING’ CREATE INDEX books_cost_desc_idx ON books (cost DESC); SELECT isbn, title, cost, category FROM books WHERE cost > 20; ISBN TITLE COST CATEGORY ---------- ------------------------------ ---------- ------------ 1915762492 HANDCRANKED COMPUTERS 21.8 COMPUTER 2147428890 SHORTEST POEMS 21.85 LITERATURE 8843172113 DATABASE IMPLEMENTATION 31.4 COMPUTER 4981341710 BUILDING A CAR WITH TOOTHPICKS 37.8 CHILDREN 9959789321 E-BUSINESS THE EASY WAY 37.9 COMPUTER 3957136468 HOLY GRAIL OF ORACLE 47.25 COMPUTER 2491748320 PAINLESS CHILD-REARING 48 FAMILY LIFE 7 rows selected. Why the output is still displayed as “ascending” order? Internally, the books table has been indexed as ‘______’ order (using pointer); however, the display is on the ‘_________’ (default) order.

38. Dr. Chen, Oracle Database System (Oracle) 38 Index on Query Optimization (conti.) -- chapter 6, (about the same as Figure 6-30; p. 199 ) -- 'BOOKS' must be in upper case SELECT table_name, index_name, index_type FROM user_indexes WHERE table_name = 'BOOKS';

39. Dr. Chen, Oracle Database System (Oracle) 39 Query Optimization: DROP INDEX DROP INDEX books_cost_idx; DROP INDEX books_cost_desc_idx; -- chapter 6, (about the same as Figure 6-30; p. 199 ) -- 'BOOKS' must be in upper case SELECT table_name, index_name, index_type FROM user_indexes WHERE table_name = 'BOOKS';

40. Dr. Chen, Oracle Database System (Oracle) 40 Summary on Optimizing Query Processing (cont.)  The indexes are defined so as to optimize the processing of SELECT statements. ;  An index is never explicitly referenced in a SELECT statement; the syntax of SQL does not allow this;  During the processing of a statement, SQL itself determines whether an existing index will be used;  An index may be created or deleted at any time;  When updating, inserting or deleting rows, SQL also maintains the indexes on the tables concerned. This means that, on the one hand, the processing time for SELECT statements is reduced, while, on the other hand, the processing time for update statements (such as INSERT, UPDATE and DELETE) can increase.

41. Dr. Chen, Oracle Database System (Oracle) 41 Your Turn … Practice the following examples (from the text)

42. Dr. Chen, Oracle Database System (Oracle) 42 CREATE INDEX Command Examples Figure 6-18 Creating an index on the Zip column

43. Dr. Chen, Oracle Database System (Oracle) 43 The Explain Plan Figure 6-20 View the explain plan indicating a full table scan

44. Dr. Chen, Oracle Database System (Oracle) 44 The Explain Plan (continued) Figure 6-21 View the explain plan indicating a full table scan

45. Dr. Chen, Oracle Database System (Oracle) 45 UNIQUE INDEX Figure 6-22 Explicitly creating a unique index -- chapter 6, Figure 6-23; p. 195 CREATE INDEX customers_zip_desc_idx ON customers (zip DESC);

46. Dr. Chen, Oracle Database System (Oracle) 46 CREATE INDEX Command Examples Figure 6-24 Creating a composite index The composite index could improve the performance of queries that include a search condition on both the Lastname and Firstname column. Generally, it is more efficient than creating two separate single- column indexes because less I/O is required to read a single index.

47. Dr. Chen, Oracle Database System (Oracle) 47 Verifying Composite Index SELECT customer#, lastname, firstname, city, state, zip FROM customers; -- chapter 6, Figure 6-24; p. 195 CREATE INDEX customer_name_idx ON customers (lastname, firstname); SELECT customer#, lastname, firstname, city, state, zip FROM customers; After tested, no significant performance can be found since it is a very small database. Any performance improvement?

48. Dr. Chen, Oracle Database System (Oracle) 48 Practice all the examples in the text. A Script file is available on the Bb (file name: Ch6Queries.sql) After completing all examples, do the HW.

49. Dr. Chen, Oracle Database System (Oracle) 49 Homework - Hands-On Assignments Read and Practice all examples on Chapters 6 1. Run the script files (in the folder \oradata\chapter5\): JLDB_Build_6.sql 2. Read Oracle assignment and create a script file Oracle_ch6_Lname_Fname.sql for questions (#1 to #5 and #9; pp.211-212) on “Hands-on Assignments”. Use appropriate COLUMN statements to produce readable outputs if needed. 3. Execute and test one problem at a time and make sure they are all running successfully. 4. When you done, spool the script files (see next slide for spooling instructions) and UPLOAD the spooled file (Oracle_ch6_Spool_Lname_Fname.txt) to Bb by the deadline. Upload the spooled file (*.txt) to the Bb (under “Assignments & Projects”) by the deadline.

50. Dr. Chen, Oracle Database System (Oracle) 50 How to Spool your Script and Output Files After you tested the script file of Oracle_ch6_Lname_Fname.sql successfully, follow the instructions below to spool both script and output files: Step 0. Run the following script file from SQL*Plus (since you have created JLDB tables) –Start c:\oradata\chapter6\JLDB_Build_6.sql 1. type the following on SQL> –Spool c:\oradata\Oracle_ch6_Spool_Lname_Fname.txt (make sure your name is entered) 2. open Oracle_ch6_Lname_Fname.sql that you already tested 3. copy and paste all the SQL commands (including all comments) to the SQL*PLUS 4. type Spool Off on the SQL> The output should contain your personal information, all SQL commands and their solution on the.txt file and saved in C: drive (oradata\ folder)

51. Dr. Chen, Oracle Database System (Oracle) 51 Summary A sequence can be created to generate a series of integers The values generated by a sequence can be stored in any table A sequence is created with the CREATE SEQUENCE command Gaps in sequences might occur if the values are stored in various tables, if numbers are cached but not used, or if a rollback occurs A value is generated by using the NEXTVAL pseudocolumn The CURRVAL pseudocolumn is NULL until a value is generated by NEXTVAL The USER_OBJECTS data dictionary object can be used to confirm the existence of all schema objects The USER_SEQUENCES data dictionary object is used to view sequence settings

52. Dr. Chen, Oracle Database System (Oracle) 52 Summary (continued) The ALTER SEQUENCE command is used to modify an existing sequence; the only settings that can’t be modified are the START WITH option and any option that would be invalid because of previously generated values The DUAL table is helpful for testing sequence value generation The DROP SEQUENCE command deletes an existing sequence An index can be created to speed up the query process DML operations are always slower when indexes exist Oracle 11g creates an index for PRIMARY KEY and UNIQUE constraints automatically An explicit index is created with the CREATE INDEX command An index can be used by Oracle 11g automatically if a query criterion or sort operation is based on a column or an expression used to create the index

53. Dr. Chen, Oracle Database System (Oracle) 53 Summary (continued) The two main structures for indexes are B-tree and bitmap The explain plan can verify whether an index is used in a query Function-based indexes are used to index an expression or the use of functions on a column or columns An index organized table is a table stored in a B-tree structure to combine the index and table into one database object Information about an index can be retrieved from the USER_INDEXES and USER_IND_COLUMNS views An index can be dropped with the DROP INDEX command An index can be renamed with the ALTER INDEX command

54. Dr. Chen, Oracle Database System (Oracle) 54 Summary (continued) Except for a name change, an index can’t be modified; it must be deleted and then re-created A synonym provides a permanent alias for a database object A public synonym is available to any database user A private synonym is available only to the user who created it A synonym is created by using the CREATE SYNONYM command A synonym is deleted by using the DROP SYNONYM command Only a user with DBA privileges can drop a public synonym

55. Dr. Chen, Oracle Database System (Oracle) 55 END OF CHAPTER 6