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Database

Database. Week 6 ERD and SQL Exercise. CREATE DB and TABLE. Create a database: CREATE DATABASE database_name Example: CREATE DATABASE my_db Create a table in a database: CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, column_name3 data_type, .... ) Example:

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Database

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  1. Database Week 6 ERD and SQL Exercise Fox MIS Spring 2011

  2. CREATE DB and TABLE • Create a database: CREATE DATABASE database_nameExample: CREATE DATABASE my_db • Create a table in a database: CREATE TABLE table_name(column_name1 data_type,column_name2 data_type,column_name3 data_type,....) Example: CREATE TABLE Persons(P_Id int,LastName varchar(255),FirstName varchar(255),Address varchar(255),City varchar(255))

  3. SQL Constraints • Constraints are used to limit the type of data that can go into a table. • Constraints can be specified when a table is created (with the CREATE TABLE statement) or after the table is created (with the ALTER TABLE statement). • NOT NULL • UNIQUE • PRIMARY KEY • FOREIGN KEY • CHECK • DEFAULT

  4. CHECK • The CHECK constraint specifies that the column "P_Id" must only include integers greater than 0. • CREATE TABLE Persons(P_Id int NOT NULL,LastName varchar(255) NOT NULL,FirstName varchar(255),Address varchar(255),City varchar(255),CHECK (P_Id>0))

  5. DEFAULT • The DEFAULT constraint is used to insert a default value into a column. • CREATE TABLE Persons(P_Id int NOT NULL,LastName varchar(255) NOT NULL,FirstName varchar(255),Address varchar(255),City varchar(255) DEFAULT 'Sandnes')

  6. PRIMARY KEY • The PRIMARY KEY constraint uniquely identifies each record in a database table. • Primary keys must contain unique values. • A primary key column cannot contain NULL values. • Each table can have only ONE primary key. • CREATE TABLE Persons(P_Id int NOT NULL,LastName varchar(255) NOT NULL,FirstName varchar(255),Address varchar(255),City varchar(255),PRIMARY KEY (P_Id)) • ALTER TABLE PersonsADD PRIMARY KEY (P_Id) • Creates primary key constraint for P_id column • Note: If you use the ALTER TABLE statement to add a primary key, the primary key column(s) must already have been declared to not contain NULL values (when the table was first created). • ALTER TABLE PersonsDROP PRIMARY KEY • Drops a PRIMARY KEY constraint

  7. FOREIGN KEY • A FOREIGN KEY in one table points to a PRIMARY KEY in another table. • CREATE TABLE Orders(O_Id int NOT NULL,OrderNo int NOT NULL,P_Id int,PRIMARY KEY (O_Id),FOREIGN KEY (P_Id) REFERENCES Persons(P_Id)) • ALTER TABLE OrdersADD FOREIGN KEY (P_Id) REFERENCES Persons(P_Id) • Create a FOREIGN KEY constraint on the "P_Id" column when the "Orders" table is already created • ALTER TABLE OrdersDROP FOREIGN KEY P_Id • Drops a FOREIGN KEY constraint

  8. ALTER TABLE • The ALTER TABLE statement is used to add, delete, or modify columns in an existing table. • ALTER TABLE table_nameADD column_name datatype constraint(optional) • ALTER TABLE table_nameCHANGE OLD_COLUMN_NAME NEW_COLUMN_NAME datatype constraint(optional) • Old column name and new column name can be the same. • ALTER TABLE table_nameDROP COLUMN column_name • ALTER TABLE PersonsADD DateOfBirth date • ALTER TABLE PersonsDROP COLUMN DateOfBirth • ALTER TABLE PersonsCHANGE DateOfBirth DateOfBirth year

  9. Exercise • Create database MISxxxearth • Create table ‘MySpring2011’ which has your course enrollment information Spring 2011 • Use { } instead of ( ) • Course ID, Course No, Course Name, Credit, Instructor Name, Day, Time • Use as many constraints as you can • Each constraint is supposed to be correct one in a logical sense • Values in some columns are supposed to be unique • There should be a primary key • Credit should be greater than zero • Add one more column ‘Department’ • Department is supposed to be ‘MIS’ by default • Insert your course information in the table • Useful command: DESCRIBE table_name

  10. ERD – Example

  11. One Possible ERD

  12. Exercise • Create database MISxxxsaturn. • Create tables for our invoice ERD example • Sample answer is in the previous slide • Decide which data type is assigned for each column • Put necessary constraints into columns • Make necessary primary and foreign keys • Insert data of three invoices (next three slides) into corresponding tables • Add yourself as a customer in the customer table • Add a person next to you as a seller in the seller table • Add your favorite book information in the product table

  13. First Invoice

  14. Second Invoice 3212 Jason Mraz 72 Spring Street New York, NY 10012 234567 6/10/2008 3930722 The Big Short Economics 20.00 1 20.00 141414 Databases R Amazing IS 100.00 2 200.00 TOTAL 220.00 Tax 13.20 Grand Total 233.20

  15. Third Invoice 3213 6/4/2008 Sunny California 610 W. Ash St San Diego , CA 92101 6/12/2008 455550 To the End of the Land Novel 20.00 5 100.00 141414 Databases R Amazing IS 100.00 1 100.00 TOTAL 200.00 Tax 12.00 Grand Total 212.00

  16. MySQL Data Types (Text Types)

  17. MySQL Data Types (Number Types)

  18. MySQL Data Types (Data Types)

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