1 A GUIDE TO ORACLE8 CHAPTER 2: Creating and ModifyingDatabaseTables 2

2 Creating and Modifying Database Tables 2  Query: Command to perform database operation  insert  modify  delete  view  Structured Query Language (SQL)  Standard query language for relational databases

3 Oracle Database Tables  Table specifications  table name  field names  field data types  field sizes  field constraints 2

4 Oracle Table and Field Names 2  1-30 characters  Alphanumeric characters and restricted symbols $ _ #  Must begin with a character  Cannot be a reserved word

5 Oracle Data Types  Data type: Specifies type of data stored in a field  Error checking  Efficient use of storage space 2

6 Character Data Types 2  VARCHAR2  Variable-length character strings  Maximum of 4,000 characters  Must specify maximum width allowed  No trailing blank spaces are added  Example declaration: student_name VARCHAR2(30)

7 Character Data Types  CHAR  Fixed-length character data  Maximum size 255 characters  Must specify maximum width allowed  Adds trailing blank spaces to pad width  Example declaration: s_gender CHAR(1) 2

8 Character Data Types 2  NCHAR  Supports 16-digit binary character codes  Used for alternate alphabets  LONG  Stores up to 2 GB of variable-length character data  Each table can have only one LONG field

9 Number Data Type  NUMBER  Stores values between and  General declaration format: variablename NUMBER(precision, scale) 2

10 Number Data Type  Number type (integer, fixed point, floating point) specified by precision and scale  Precision: Total number of digits on either side of the decimal point  Scale: Number of digits to right of decimal point 2

11 Integer Numbers  Whole number with no digits to right of decimal point  Precision is maximum width  Scale is omitted  Sample declaration: s_age NUMBER (2) 2

12 Fixed-Point Numbers  Contains a specific number of decimal places  Precision is maximum width  Scale is number of decimal places  Sample declaration: item_price NUMBER(5, 2) 2

13 Floating-Point Numbers  Contains a variable number of decimal places  Precision and scale are omitted  Sample declaration: s_GPA NUMBER 2

14 Date Data Type  DATE  Stores dates from 1/1/4712 BC to 12/31/4712 AD  Default date format: DD-MON-YY  Example: 05-JUN-01  Sample declaration: s_dob DATE 2

15 Date Data Type 2  DATE data type also stores time values  If no time value is given when a date is inserted, default value is 12:00:00 AM  If no date value is given when a time is inserted, default date is first day of current month

16 Large Object (LOB) Data Types  BLOB: Binary LOB, up to 4 GB of binary data in database  CLOB: Character LOB, up to 4 GB of character data in database  BFILE: Reference to binary file stored in operating system  NCLOB: Character LOB supporting 16-bit character codes 2

17 Format Masks 2  Specify input and output formats for data values  Common NUMBER format masks Format MaskFormatted Data 99,99912,345 $99,999.99$12, ,999PR 99,999MI-12,345 $99,999.99PR

18 Format Masks  Common DATE format masks Format MaskFormatted Data DD-MON-YY05-JUN-01 DD-MON-YYYY05-JUN-2001 MM/DD/YY06/05/2001 HH:MI AM02:30 PM MONTH DAY, YYYYJUNE 5, 2001 MM/DD/YY HH:MI AM06/05/01 02:30 PM 2

19 Format Masks 2  Common character format masks with embedded characters Format MaskFormatted Data  Social Security Number: FM999”-”999”-”  Phone Number: FM”(“999”) “999”-”9999(715)

20 Integrity Constraints  Used to define primary and foreign keys  Constraint name: Internal name used by DMBS to identify the constraint  Constraint name convention:  tablename_fieldname_constraintID  Constraint ID values:  Primary key: PK  Foreign key: FK 2

21 Primary Key Constraints  Defining a primary key: CONSTRAINT PRIMARY KEY  Example: sid NUMBER(6) CONSTRAINT student_sid_pk PRIMARY KEY 2

22 Primary Key Constraints  Defining a composite primary key: CONSTRAINT PRIMARY KEY (field1, field2)  Example: sid NUMBER(6), course_id NUMBER(6), grade NUMBER, CONSTRAINT enrollment_sid_course_id_pk PRIMARY KEY (sid, course_id) 2

23 Foreign Key Constraints  Defining a foreign key: CONSTRAINT REFERENCES ( )  Example: advisorid NUMBER(6) CONSTRAINT student_advisorid_fk REFERENCES faculty(fid) 2

24 Value Constraints  Restricts data values that can be inserted into a field  Types  Check condition: Restricts to specific values  example: s_gender (M or F)  NOT NULL: Specifies that a field cannot be NULL 2

25 Defining Value Constraints  Check condition  CONSTRAINT CHECK s_gender CHAR(1) CONSTRAINT student_s_gender_cc CHECK ((s_gender = ‘M’) OR (s_gender = ‘F’))  Not NULL  CONSTRAINT NOT NULL s_name VARCHAR2(30) student_s_name_nn NOT NULL 2

26 SQL*Plus 2  Oracle SQL command line utility  Starting SQL*Plus

27 SQL*Plus 2  All commands must be terminated with a semicolon  Use a text editor and copy and paste commands  Character data is case sensitive and must be in single quotes ‘M’ ‘Sarah’

28 Creating a Database Table  CREATE TABLE (, <field2 declaration, …); CREATE TABLE mystudent (sid NUMBER(6) CONSTRAINT mystudent_sid_pk PRIMARY KEY, s_name VARCHAR2(30) CONSTRAINT mystudent_s_name_nn NOT NULL); 2

29 Other Table Operations  Viewing a table’s structure DESCRIBE mystudent;  Viewing constraint information SELECT CONSTRAINT_NAME FROM USER_CONSTRAINTS WHERE TABLE_NAME = ‘MYSTUDENT’ ;  Deleting a table DROP TABLE mystudent; 2

30 Modifying Tables  Prohibited  Changing the table name  Changing a column name  Unrestricted  Adding a new column  Deleting a primary key or foreign key constraint 2

31 Modifying Tables  Restricted (allowed only if existing data fits new specification)  Changing a column’s data type, size, and default value  Adding a primary key constraint  Adding a foreign key constraint  Adding a CHECK CONDITION constraint  Adding a NOT NULL constraint 2

32 Exiting SQL*Plus  Type exit at SQL> prompt or  Click Close button 2