1. 5 Chapter 5 Structured Query Language (SQL1) Revision

2. 5 2 In this lecture, you will learn: Data definition commands Data manipulation commands

3. 5 3 ( Defining database, table structures, table relationship)

4. 5 4 Data Definition Commands Create database structure –Holds all tables and is a collection of physical files stored on disk –DBMS automatically creates tables to store metadata CREATE DATABASE Example: CREATE DATABASE TDB2111

5. 5 5 Creating Table Structure Tables store end-user data May be based on data dictionary entries CREATE TABLE ( );

6. 5 6 Data Type Data Types include: CHAR, INTEGER, VARCHAR, DECIMAL, DATE (see page 110) Some Examples: CHAR(25), INTEGER, SMALLINT, DECIMAL(9,2), DATE

7. 5 7 SQL Integrity Constraints Adherence to entity integrity and referential integrity rules is crucial –Entity integrity enforced automatically if primary key specified in CREATE TABLE command sequence –Referential integrity can be enforced in specification of FOREIGN KEY –Other specifications to ensure conditions met: ON DELETE RESTRICT ON UPDATE CASCADE

8. 5 8

9. 5 9 (retrieve, add, delete, update data)

10. 5 10 Data Manipulation Commands Common SQL Commands Table 5.3

11. 5 11 Listing Table Contents and Other Commands INSERT command makes data entry UPDATE command makes data entry corrections ROLLBACK command restores database back to previous condition if COMMIT hasn’t been used DELETE command removes table row Allows table contents to be listed SELECT FROM ;

12. 5 12 Data Entry (INSERT) Enters data into a table INSERT INTO VALUES (attribute 1 value, attribute 2 value, … etc.); INSERT INTO BOOK VALUES (‘0180’,’Shyness’,’PSY’,7.65 ); values of attributes must be listed in the correct order/sequence values of character attributes are enclosed in ‘ ‘

13. 5 13 Commit & Rollback Saves changes to disk COMMIT ; COMMIT Book; if you know something has gone wrong ROLLBACK; takes you back to the last COMMIT

14. 5 14 Update (modify data) UPDATE BOOK SET Book_Type=‘MYS’, Book_Price=9.95 WHERE Book_Code=‘0180’; can set the value of more that one attribute in a single UPDATE statement by separating the list of attributes and their values with commas

15. 5 15 Delete (Remove data) DELETE FROM BOOK WHERE Book_Code=‘0180’; the WHERE clause does not have to be written in terms of the primary key DELETE FROM BOOK WHERE Book_Type=‘PSY’; would delete all the psy books Note: DELETE FROM BOOK WHERE Pub_Code EXISTS; deletes all tuples where there is a non-null Pub_Code

16. 5 16 SELECT (retrieve certain/all data) SELECT * FROM BOOK; SELECT Book_Code, Book_Title FROM BOOK; SELECT * FROM BOOK WHERE Book_Code=‘0181’; SELECT Book_Code, Pub_Name FROM BOOK, PUBLISHER WHERE BOOK.Pub_Code = PUBLISHER.PubCode