1. 1 Creating and Maintaining Database Objects Part 1 Database Systems

2. 2  Script: text file that contains a sequence of SQL commands  Running a script: SQL> START path_to_script_file;  Path cannot contain any blank spaces SQL Scripts

3. 3  Syntax: INSERT INTO tablename VALUES (column1_value, column2_value, …);  You must insert a value or a NULL placeholder for every field  Fields must be entered in the order they appear in the table when you issue the DESC command Inserting a Value Into Every Field in a Record

4. 4 Example:

5. 5  Command to insert values for selected record fields: INSERT INTO tablename (column1_name, column2_name, …) VALUES (column1_value, column2_value, …); Inserting Selected Table Fields

6. 6  Example: Inserting Selected Table Fields

7. 7  Date values must be converted from characters to dates using the TO_DATE function and a format mask  Example: Inserting Date Values

8. 8  Must be enclosed in single quotes  Is case-sensitive  To insert a string with a single quote, type the single quote twice  Example: 'Mike''s Motorcycle Shop' Inserting Text Data

9. 9  Transaction  Logical unit of work consisting of one or more SQL DML commands  INSERT, UPDATE, DELETE  All transaction commands must succeed or none can succeed  Transaction results are not visible to other users until they are “committed” to the database  Until a transaction is committed, it can easily be “rolled back” (undone) Transactions

10. 10  A transaction starts when you type one or more commands in SQL*Plus  A transaction ends when you issue either the COMMIT or ROLLBACK command SQL>COMMIT; SQL>ROLLBACK; Transactions

11. 11 Committing and Rolling Back Data COMMIT Makes transaction command changes permanent in the database and visible to other users ROLLBACK Rolls back transaction command changes and restores database to its state before the transaction

12. 12  Used to mark individual sections of a transaction  You can roll back a transaction to a savepoint Savepoints

13. 13  Syntax: UPDATE tablename SET column1 = new_value, column2 = new_value, … WHERE search_condition;  Records can be updated in only one table at a time  Can update multiple records if they all match the search condition Updating Records

14. 14  Format: WHERE fieldname operator expression  Operators  Equal (=)  Greater than, Less than (>, <)  Greater than or Equal to (>=)  Less than or Equal to (<=)  Not equal (, !=, ^=  LIKE  BETWEEN  IN  NOT IN Search Conditions

15. 15 WHERE s_name = ‘Sarah’ WHERE s_age > 18 WHERE s_class <> ‘SR’  Text in single quotes is case sensitive Search Condition Examples

16. 16  Syntax: DELETE FROM tablename WHERE search_condition;  Deletes multiple records if search condition specifies multiple records  If search condition is omitted, all table records are deleted  You can’t delete a record if it contains a primary key value that is referenced as a foreign key Deleting Records

17. 17 Truncating Tables Removes all table data without saving any rollback information Advantage: fast way to delete table data Disadvantage: can’t be undone Syntax: TRUNCATE TABLE tablename;

18. 18  Sequential list of numbers that is automatically generated by the database  Used to generate values for surrogate keys Sequences

19. 19  Syntax: CREATE SEQUENCE sequence_name [optional parameters];  Example: CREATE SEQUENCE f_id_sequence START WITH 200; Creating Sequences

20. 20 Viewing Sequence Information Query the SEQUENCE Data Dictionary View:

21. 21 Pseudocolumns Acts like a column in a database query Actually a command that returns a specific values Used to retrieve: Current system date Name of the current database user Next value in a sequence

22. 22 Pseudocolumn Examples Pseudocolumn Name Output CURRVALMost recently retrieved sequence value NEXTVALNext value in a sequence SYSDATECurrent system date from database server USERUsername of current user

23. 23  Retrieving the current system date : SELECT SYSDATE FROM DUAL; Retrieving the name of the current user: SELECT USER FROM DUAL;  DUAL is a system table that is used with pseudocolumns Using Pseudocolumns

24. 24  Accessing the next value in a sequence: sequence_name.NEXTVAL  Inserting a new record using a sequence: INSERT INTO my_faculty VALUES (f_id_sequence.nextval, ‘Professor Jones’); Using Pseudocolumns With Sequences

25. 25 Permissions that you can grant to other users to allow them to access or modify your database objects Granting object privileges: GRANT privilege1, privilege2, … ON object_name TO user1, user 2, …; Revoking object privileges: REVOKE privilege1, privilege2, … ON object_name FROM user1, user 2, …; Object Privileges

26. 26 Examples of Object Privileges Object TypePrivilegeDescription Table, Sequence ALTERAllows user to change object’s structure using the ALTER command Table, Sequence DROPAllows user to drop object Table, Sequence SELECTAllows user to view object TableINSERT, UPDATE, DELETE Allows user to insert, update, delete table data Any database object ALLAllows user to perform any operation on object

27. 27 Granting and Revoking Object Privileges

28. 28  Syntax: SELECT column1, column2, … FROM tablename WHERE search_condition; Retrieving Data From a Single Table

29. 29  To retrieve every column in a table: SELECT * FROM …  To retrieve every record in a table, omit the search condition SELECT column1, column2, … FROM tablename; Retrieving Data From a Single Table

30. 30 Qualifying Table Names If you retrieve data from a table that is owned by another user, you must qualify the table name by prefacing it with the owner’s name

31. 31  Sometimes queries retrieve duplicate records  To suppress duplicate outputs, use the DISTINCT qualifier : SELECT DISTINCT column1, column2, … FROM... Suppressing Duplicate Records

32. 32  Combining search conditions  AND: both conditions must be true  OR: either condition can be true  Combining AND and OR in a single operation  AND comparisons are evaluated first  Always use parentheses to force conditions to be evaluated in the correct order Using Multiple Search Conditions

33. 33  NULL: not defined  Use IS NULL search condition SELECT s_name, s_class FROM my_students WHERE s_class IS NULL; Searching for NULL Records

34. 34  Use IS NOT NULL operator SELECT s_name, s_age FROM my_students WHERE s_class IS NOT NULL; Searching for NOT NULL Records

35. 35 Using the IN and NOT IN Operators IN retrieves all values where the search column value matches a set of values SELECT * FROM enrollment WHERE grade IN (‘A’, ‘B’);

36. 36 Using the IN and NOT IN Operators NOT IN retrieves all values where the search column value matches a set of values SELECT * FROM enrollment WHERE grade NOT IN (‘A’, ‘B’);

37. 37 Using the LIKE Operator Performs inexact searches by matching part of a character string WHERE fieldname LIKE character_string;

38. 38 Using the LIKE Operator Character string must be in single quotes and use wildcard characters % represents multiple wildcard characters _ represents a single wildcard character Wildcard characters can be placed at beginning or end of string Examples: WHERE s_class LIKE ‘_R’; WHERE s_name LIKE ‘J%’;

39. 39  Use the ORDER BY clause  Specify sort key, which is column by which output is sorted SELECT s_name, s_age FROM my_students ORDER BY s_age; Sorting Query Output

40. 40  Default sort order  Numerical: ascending  Character: A - Z  Date: oldest - newest  To force the sort order: use ASC or DESC  Example SELECT s_name, s_age FROM my_students ORDER BY s_age DESC; Sorting Query Data

41. 41  Arithmetic operations on retrieved data  Addition (+)  Subtraction (-)  Multiplication (*)  Division (/)  Example: SELECT inv_id, qoh*price FROM inventory; Using Calculations in Queries

42. 42  ABS - absolute value  CEIL – rounds a number up to the next integer  FLOOR – rounds a number down to the previous integer  MOD – returns the remainder of a number and a divisor  POWER - raises a number to an exponent  ROUND - rounds a number  SQRT – returns the square root of a value  TRUNC - truncates a number to the nearest whole number Single-Row Number Functions

43. 43  Example: SELECT s_name, TRUNC((SYSDATE - s_dob)/365) FROM my_students; Using Single-Row Number Functions

44. 44  CONCAT – joins 2 character strings  INITCAP – returns a string with the initial letter only uppercase  LENGTH – returns the length of a string  LPAD, RPAD – returns a string with a specific number of characters added on the left or right side  LTRIM, RTRIM – returns a string with all instances of a specific character trimmed from the left or right side  REPLACE – replaces all instances of a character with another character  UPPER/LOWER – returns a string in all upper/lower case letters Single-Row Character Functions

45. 45  Example: SELECT UPPER(s_name) FROM my_students; Using Single-Row Character Functions

46. End of Lecture