Tonight’s Lecture

chapter 3

A Guide to MySQL 2

Using MySQL Reference Manual to Get Help

• Can access online

• http://dev.mysql.com/doc/refman/5.0/en/

A Guide to MySQL 3

Describing a Table

In Oracle

DESC table_name

example: DESC h_book

DDL

• Stands for Data Definition Language– create statements– drop statements– alter statements

A Guide to MySQL 6

Creating a Database

• Must create a database before creating tables

• Use CREATE DATABASE command

• Include database name

A Guide to MySQL 7

Changing the Default Database

• Default database: database to which all subsequent commands pertain

• USE command, followed by database name:– Changes the default database

– Execute at the start of every session

You’re changing your default database by selecting your user database from the drop down in PhpMyAdmin

A Guide to MySQL 9

Creating a Table• Describe the layout of each table in the database

• Use CREATE TABLE command

• TABLE is followed by the table name

• Follow this with the names and data types of the columns in the table

• Data types define type and size of data

A Guide to MySQL 10

Table and Column Name Restrictions

• Names cannot exceed 18 characters

• Must start with a letter

• Can contain letters, numbers, and underscores (_)

• Cannot contain spaces

Avoid using reserved words as names of your database objects

Reserved words can differ from database platform to database platform

MySQL reserved word examples - select- numeric- database- group

A Guide to MySQL 12

Implementation of Nulls

• Use NOT NULL clause in CREATE TABLE command to exclude the use of nulls in a column

• Default is to allow null values

• If a column is defined as NOT NULL, system will reject any attempt to store a null value there

CREATE TABLE a_marina( MARINA_NUM char(4) NOT NULL, NAME char(20) NULL, ADDRESS char(15) NULL, CITY char(15) NULL, STATE char(2) NULL, ZIP char(5) NULL, PRIMARY KEY (MARINA_NUM))

Field Type Null Key Default ExtraMARINA_NUM char(4) NO PRI NAME char(20) YES ADDRESS char(15) YES CITY char(15) YES STATE char(2) YES ZIP char(5) YES

What will this SQL statement do?

CREATE TABLE a_marina( MARINA_NUM char(4) NOT NULL, NAME char(20), ADDRESS char(15), CITY char(15), STATE char(2), ZIP char(5), PRIMARY KEY (MARINA_NUM))

Field Type Null Key Default ExtraMARINA_NUM char(4) NO PRI NAME char(20) YES ADDRESS char(15) YES CITY char(15) YES STATE char(2) YES ZIP char(5) YES

What will this SQL statement do?

CREATE TABLE a_marina( MARINA_NUM char(4) NOT NULL, NAME char(20), ADDRESS char(15), CITY char(15), STATE char(2), ZIP char(5))

Field Type Null Key Default ExtraMARINA_NUM char(4) NO NAME char(20) YES ADDRESS char(15) YES CITY char(15) YES STATE char(2) YES ZIP char(5) YES

What will this SQL statement do?

CREATE TABLE a_marina( MARINA_NUM char(4) NOT NULL, NAME char(20), ADDRESS char(15), CITY char(15), STATE char(2), ZIP)

What will this SQL statement do?

ERROR

We did not specify a datatype for the column ZIP

Field Type Null Key Default ExtraOWNER_NUM char(4) NO PRI LAST_NAME char(50) YES FIRST_NAME char(20) YES ADDRESS char(15) YES CITY char(15) YES STATE char(2) YES ZIP char(5) YES

Write the SQL that will create an A_OWNER table with the following structure:

CREATE TABLE a_owner( OWNER_NUM char(4) NOT NULL, LAST_NAME char(50) NULL, FIRST_NAME char(20) NULL, ADDRESS char(15) NULL, CITY char(15) NULL, STATE char(2) NULL, ZIP char(5) NULL, PRIMARY KEY (OWNER_NUM))

Field Type Null Key Default Extraemployee_id varchar(10) YES name varchar(100) YES manager_id varchar(10) YES

CREATE TABLE employees( employee_id varchar(10) NULL, name varchar(100) NULL, manager_id varchar(10) NULL)

Write the SQL that will create an EMPLOYEES table with the following structure:

Field Type Null Key Default ExtraORDER_NUM char(5) NO PRI PART_NUM char(4) NO PRI NUM_ORDERED decimal(3,0) YES QUOTED_PRICE decimal(6,2) YES

CREATE TABLE p_order_line( ORDER_NUM char(5) NOT NULL, PART_NUM char(4) NOT NULL, NUM_ORDERED decimal(3,0) NULL, QUOTED_PRICE decimal(6,2) NULL, PRIMARY KEY (ORDER_NUM,PART_NUM))

Write the SQL that will create an P_ORDER_LINE table with the following structure:

Field Type Null Key Default ExtraBOOK_CODE char(4) NO PRI BRANCH_NUM decimal(2,0) NO PRI 0 ON_HAND decimal(2,0) YES

CREATE TABLE h_inventory( BOOK_CODE char(4) NOT NULL, BRANCH_NUM decimal(2,0) NOT NULL default 0, ON_HAND decimal(2,0) NULL, PRIMARY KEY (BOOK_CODE,BRANCH_NUM))

Write the SQL that will create an H_INVENTORY table with the following structure:

CREATE TABLE h_book( BOOK_CODE char(4) NOT NULL, TITLE char(40) NULL, PUBLISHER_CODE char(3) NULL, TYPE char(3) NULL, PRICE decimal(4,2) NULL, PAPERBACK char(1) NULL, PRIMARY KEY (BOOK_CODE))

Write the SQL that will create an H_BOOK table with the following structure:

Field Type Null Key Default ExtraBOOK_CODE char(4) NO PRI TITLE char(40) YES PUBLISHER_CODE char(3) YES TYPE char(3) YES PRICE decimal(4,2) YES PAPERBACK char(1) YES

CREATE TABLE p_rep( REP_NUM char(2) NOT NULL, LAST_NAME char(15) NULL, FIRST_NAME char(15) NULL, STREET char(15) NULL, CITY char(15) NULL, STATE char(2) NULL, ZIP char(5) NULL, COMMISSION decimal(7,2) NULL, RATE decimal(3,2) NULL, PRIMARY KEY (REP_NUM))

Write the SQL that will create an P_REP table with the following structure:

Field Type Null Key Default ExtraREP_NUM char(2) NO PRI LAST_NAME char(15) YES FIRST_NAME char(15) YES STREET char(15) YES CITY char(15) YES STATE char(2) YES ZIP char(5) YES COMMISSION decimal(7,2) YES RATE decimal(3,2) YES

A Guide to MySQL 23

Dropping a Table

• Can correct errors by dropping (deleting) a table and starting over

• Useful when table is created before errors are discovered

• Command is followed by the table to be dropped and a semicolon

• Any data in table also deleted

drop table a_owner

be careful with drop statements

What is DDL?

A Guide to MySQL 26

Adding Rows to a Table

• INSERT command:

– INSERT INTO followed by table name

– VALUES command followed by specific values in parentheses

– Values for character columns in single quotation marks

A Guide to MySQL 27

The Insert Command