Fox MIS Spring 2011 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: CREATE TABLE Persons ( P_Id int, LastName varchar(255), FirstName varchar(255), Address varchar(255), City varchar(255) )

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

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) )

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' )

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 Persons ADD 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 Persons DROP PRIMARY KEY –Drops a PRIMARY KEY constraint

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 Orders ADD 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 Orders DROP FOREIGN KEY P_Id –Drops a FOREIGN KEY constraint

ALTER TABLE The ALTER TABLE statement is used to add, delete, or modify columns in an existing table. ALTER TABLE table_name ADD column_name datatype constraint(optional) ALTER TABLE table_name CHANGE OLD_COLUMN_NAME NEW_COLUMN_NAME datatype constraint(optional) –Old column name and new column name can be the same. ALTER TABLE table_name DROP COLUMN column_name ALTER TABLE Persons ADD DateOfBirth date ALTER TABLE Persons DROP COLUMN DateOfBirth ALTER TABLE Persons CHANGE DateOfBirth DateOfBirth year

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

ERD – Example

One Possible ERD

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

First Invoice

Second Invoice /10/2008 Jason Mraz 72 Spring Street New York, NY Jason Mraz 72 Spring Street New York, NY The Big Short Economics Databases R Amazing IS TOTAL Tax Grand Total The Big Short Economics Databases R Amazing IS TOTAL Tax Grand Total

Third Invoice /4/2008 6/12/2008 Sunny California 610 W. Ash St San Diego, CA Sunny California 610 W. Ash St San Diego, CA To the End of the Land Novel Databases R Amazing IS TOTAL Tax Grand Total To the End of the Land Novel Databases R Amazing IS TOTAL Tax Grand Total

MySQL Data Types (Text Types) Data typeDescription CHAR(size)Holds a fixed length string (can contain letters, numbers, and special characters). The fixed size is specified in parenthesis. Can store up to 255 characters VARCHAR(size)Holds a variable length string (can contain letters, numbers, and special characters). The maximum size is specified in parenthesis. Can store up to 255 characters. Note: If you put a greater value than 255 it will be converted to a TEXT type TINYTEXTHolds a string with a maximum length of 255 characters TEXTHolds a string with a maximum length of 65,535 characters BLOBFor BLOBs (Binary Large OBjects). Holds up to 65,535 bytes of data MEDIUMTEXTHolds a string with a maximum length of 16,777,215 characters MEDIUMBLOBFor BLOBs (Binary Large OBjects). Holds up to 16,777,215 bytes of data LONGTEXTHolds a string with a maximum length of 4,294,967,295 characters LONGBLOBFor BLOBs (Binary Large OBjects). Holds up to 4,294,967,295 bytes of data ENUM(x,y,z,et c.) Let you enter a list of possible values. You can list up to values in an ENUM list. If a value is inserted that is not in the list, a blank value will be inserted. Note: The values are sorted in the order you enter them. SETSimilar to ENUM except that SET may contain up to 64 list items and can store more than one choice

MySQL Data Types (Number Types) Data typeDescription TINYINT(size)-128 to 127 normal. 0 to 255 UNSIGNED*. The maximum number of digits may be specified in parenthesis SMALLINT(size) to normal. 0 to UNSIGNED*. The maximum number of digits may be specified in parenthesis MEDIUMINT(size) to normal. 0 to UNSIGNED*. The maximum number of digits may be specified in parenthesis INT(size) to normal. 0 to UNSIGNED*. The maximum number of digits may be specified in parenthesis BIGINT(size) to normal. 0 to UNSIGNED*. The maximum number of digits may be specified in parenthesis FLOAT(size,d)A small number with a floating decimal point. The maximum number of digits may be specified in the size parameter. The maximum number of digits to the right of the decimal point is specified in the d parameter DOUBLE(size,d)A large number with a floating decimal point. The maximum number of digits may be specified in the size parameter. The maximum number of digits to the right of the decimal point is specified in the d parameter DECIMAL(size,d)A DOUBLE stored as a string, allowing for a fixed decimal point. The maximum number of digits may be specified in the size parameter. The maximum number of digits to the right of the decimal point is specified in the d parameter

MySQL Data Types (Data Types) Data typeDescription DATE()A date. Format: YYYY-MM-DD Note: The supported range is from ' ' to ' ' DATETIME()*A date and time combination. Format: YYYY-MM-DD HH:MM:SS Note: The supported range is from ' :00:00' to ' :59:59' TIMESTAMP()*A timestamp. TIMESTAMP values are stored as the number of seconds since the Unix epoch (' :00:00' UTC). Format: YYYY-MM-DD HH:MM:SS Note: The supported range is from ' :00:01' UTC to ' :14:07' UTC TIME()A time. Format: HH:MM:SS Note: The supported range is from '-838:59:59' to '838:59:59' YEAR()A year in two-digit or four-digit format. Note: Values allowed in four-digit format: 1901 to Values allowed in two-digit format: 70 to 69, representing years from 1970 to 2069