Sql database object

1
Database SystemsDatabase Systems
Creating and Modifying
Database Objects

2
Database Objects
 An Oracle database consists of multiple
user accounts
 Each user account owns database
objects
 Tables
 Views
 Stored programs
 Etc.

3
 Query: command to perform
operation on database object
 Create
 Modify
 View
 Delete
 Structured Query Language (SQL)
 Standard query language for
relational databases
Database Queries

4
SQL Command Types
 Data Definition Language (DDL)
 Used to create and modify the structure of
database objects
 Data Manipulation Language (DML)
 Used to insert, update, delete, and view
database data

5
DDL Commands
 Used to create and modify the structure
of database objects
 CREATE
 ALTER
 DROP
 DDL commands execute as soon as
they are issued, and do not need to be
explicitly saved

6
DML Commands
 Used to insert, view, and modify database
data
 INSERT
 UPDATE
 DELETE
 SELECT
 DDL commands need to be explicitly saved or
rolled back
 COMMIT
 ROLLBACK

7
User Accounts
 Each Oracle database user has a user
schema
 Area in the database where the user’s
database objects are stored
 Identified by a unique username and
protected by a password
 Each user schema is granted specific
privileges

8
Types of Database Privileges
 System Privileges
 Control the operations that the user can perform
within the database

Connecting to the database, creating new tables,
shutting down the database, etc.
 Object Privileges
 Granted on individual database objects
 Controls operations that a user can perform on a
specific object (insert data, delete data, etc.)
 When you create an object in your user schema,
you can then grant object privileges on that object
to other database users

9
Oracle Naming Standard
 Oracle database objects must adhere to
the Oracle Naming Standard
 1 to 30 characters long
 Must begin with a character
 Can contain characters, numbers, and the
symbols $, _, and #

10
Creating New User Accounts
 Done by DBA
 Syntax:
CREATE username IDENTIFIED BY password;

11
Example Oracle System
Privileges
Privilege Leve
l
Purpose
CREATE SESSION User Connecting to database
CREATE TABLE User Creating tables in current user schema
DROP TABLE User Dropping tables in current user
schema
UNLIMITED
TABLESPACE
User Allows user to create schema objects
using as much space as needed
CREATE USER DBA Creating new users
GRANT ANY PRIVILEGE DBA Granting system privileges to users
CREATE ANY TABLE DBA Creating tables in any user schema
DROP ANY TABLE DBA Dropping tables in any user schema

12
Granting System Privileges
 Done by DBA
 Syntax:
GRANT privilege1, privilege2, … TO username;

13
Database Roles
 Role is a database object that can be
assigned system privileges
 Role is then assigned to a user, and the
user inherits the role’s privileges
 Used to easily assign groups of related
privileges to users

14
Creating Roles
 Syntax:
CREATE ROLE role_name;

15
Assigning Privileges to a Role
 Syntax:
GRANT privilege1, privilege2, …
TO role_name;

16
Assigning a Role to a User
 Syntax:
GRANT role_name TO user_name;

17
Revoking System Privileges
 Syntax:
REVOKE privilege1, privilege2, …
FROM username;

18
Administering System
Privileges
 To be able to grant system privileges to
other users, a user account must have
been granted the privilege WITH
ADMIN OPTION

19
 To create a table, you must
specify:
 Table name
 Field names
 Field data types
 Field sizes
 Constraints
Defining Database Tables

20
 Must follow the Oracle Naming
Standard
 Each table in a user schema must
have a unique name within that
user schema
 Each field in a table must have a
unique name within that table
Table and Field Names

21
 Data type: specifies type of data
stored in a field
 Date, character, number, etc.
 Uses
 Error checking
 Efficient use of storage space
Oracle Data Types

22
 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)
Oracle Character Data Types

23
 CHAR
 Fixed-length character data
 Maximum size 2000 characters
 Must specify maximum width allowed
 Adds trailing blank spaces to pad width
 Example declaration:
student_gender CHAR(1)
Character Data Types

24
 NCHAR
 Supports 16-digit binary character
codes
 Used for alternate alphabets
Character Data Types

25
 NUMBER
 stores values between 10-130
and 10126
 General declaration format:
variable_name NUMBER(precision, scale)
Number Data Type

26
 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
NUMBER Data Types

27
 Whole number with no digits to
right of decimal point
 Precision is maximum width
 Scale is omitted
 Sample declaration:
s_age NUMBER (2)
Integer Numbers

28
 Contain a specific number of
decimal places
 Precision is maximum width
 Scale is number of decimal places
item_price NUMBER(5, 2)
Fixed Point Numbers

29
 Contain a variable number of
decimal places
 Precision and scale are omitted
s_GPA NUMBER
Floating Point Numbers

30
 DATE
 Stores dates from 1/1/4712 BC to
12/31/4712 AD
 Stores both a date and time component
 Default date format:
DD-MON-YY HH:MI:SS AM
 example: 05-JUN-03 12:00:00 AM
s_dob DATE
Date Date Type

31
 If no time value is given when a
new date is inserted, default value
is 12:00:00 AM
 If no date value is given when a
new time is inserted, default date
is first day of current month
Specifying Date and Time
Values

32
Large Object (LOB) Data
Types
 Binary Large Object (BLOB)
 Stores up to 4 GB of binary data
 Character Large Object (CLOB)
 Stores up to 4 GB of character data
 BFILE
 Stores a reference to a binary file maintained in
the operating system
 NCLOB
 Character LOB that supports 16-bit character code

33
Declaring LOB Data Fields
 Item size is not specified
 Examples:
item_image BLOB
item_image BFILE

34
 Syntax:
CREATE TABLE table_name
( fieldname1 datatype,
fieldname2 datatype, …);
 Example:
CREATE TABLE my_students
( s_id NUMBER(6),
s_name VARCHAR2(30),
s_dob DATE,
s_class CHAR(2));
Creating a Database Table

35
Constraints
 Rules that restrict the values that can
be inserted into a field
 Types of constraints
 Integrity: define primary and foreign keys
 Value: specify values or ranges of values
that can be inserted

36
Constraint Levels
 Table constraint
 Restricts the value of a field with respect to
all other table records
 Example: primary key value must be
unique for each record
 Column constraint
 Restricts values in a specific column
 Example: values in an S_GENDER field
must be ‘M’ or ‘F’

37
 Internal name used by DBMS to identify the
constraint
 Each constraint name in a user schema
must be unique
 If you do not name a constraint, the system
will automatically generate an unintuitive
name
Constraint Names

38
 Constraint naming convention:
tablename_fieldname_constraintID
 Constraint ID values:
 Primary key: pk
 Foreign key: fk
 Check condition: cc
 Not NULL: nn
 Unique: uk
 Example constraint name:
my_students_s_id_pk
Constraint Names

39
 Table-level
 Defining a primary key:
CONSTRAINT constraint_name PRIMARY KEY
 Example:
s_id NUMBER(6)
CONSTRAINT student_s_id_pk PRIMARY KEY
Primary Key Constraints

40
 Can be defined when field is declared

41
 Can also be defined after all table field
definitions are completed

42
 Syntax:
CONSTRAINT constraint_name
PRIMARY KEY (field1, field2)
 Must be defined after fields that compose
key are defined
Composite Primary Keys

43
 Table-level
 Can only be defined after field is defined as a
primary key in another table
 Syntax:
CONSTRAINT constraint_name
REFERENCES primary_key_table_name
(field_name)
Foreign Key Constraints

44
 Can be defined when field is declared

45
 Can also be defined after all table field
definitions are completed

46
 Column-level
 Restricts data values that can be inserted
in a field
 In general, avoid value constraints
because they make the database very
inflexible
Value Constraints

47
 Check condition: restricts to specific values
 Example: s_gender (M or F)
CONSTRAINT my_students_s_gender_cc
CHECK (s_gender = ‘M’) OR (s_gender = ‘F’)
 Not NULL: specifies that a field cannot be
NULL
 Example:
CONSTRAINT my_students_s_dob_nn
NOT NULL
Types of Value Constraints

48
 Default: specifies a default value that is inserted
automatically
 Example:
s_state CHAR(2) DEFAULT ‘WI’
 Unique
 Table constraint
 Specifies that a non-primary key field must have a unique
value
CONSTRAINT consultant_c_email_uk UNIQUE (c_email)
Types of Value Constraints

49
 Oracle SQL command line utility for
issuing SQL commands
 Starting SQL*Plus
SQL*Plus

50
 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’
Using SQL*Plus

51
 Type exit at SQL> prompt
or
 Click Close button on SQL*Plus
window
Exiting SQL*Plus

52
 Ora.hlp file
 Oracle Technology Network
(OTN)
 http://otn.oracle.com
Oracle Help Resources

53
 Viewing a table’s structure
DESCRIBE table_name;
Viewing Table Information

54
Oracle Data Dictionary
 Contains tables that describe the database
structure
 Is in the SYSTEM user schema
 Is automatically updated as users create and
modify tables
 Cannot be updated directly
 Contains views that allow users to retrieve
information about the database structure

55
Data Dictionary Views
 Views present data in different formats
depending on the privileges of the user
 USER: shows all objects belonging to the
current user
 ALL: shows all objects belonging to the
current user, as well as objects current
user has privileges to manipulate
 DBA: allows users with DBA privileges to
view objects of all database users

56
Querying the Data Dictionary
Views
 Syntax:
SELECT field1, field2, …
FROM privilege_viewname;

57
Summary of Oracle
Data Dictionary Views
OBJECTS All database objects
TABLES Database tables
INDEXES Table indexes created to improve query
performance
VIEWS Database views
SEQUENCES Sequences created to automatically
generate surrogate key values
USERS Database users
CONSTRAINTS Table constraints
CONS_CONSTRAINT
S
Table columns that have constraints
IND_COLUMNS Indexed columns
TAB_COLUMNS All table columns

58
 Unrestricted actions
 Renaming tables
 Adding new columns
 Increasing column sizes
 Dropping columns
 Dropping constraints
Modifying Tables

59
 Restricted actions
 Dropping tables

Only allowed if table does not contain any fields that
are referenced as foreign keys, or if foreign key
constraints are dropped
 Changing a column’s data specification

Only allowed if existing data is compatible with new
data specification
 Decreasing column sizes

Only allowed if column does not contain any data
 Adding constraints

Only allowed if existing data meets requirements of
new constraint
Modifying Tables

60
Altering Tables
 Adding a new field:
ALTER TABLE tablename
ADD (fieldname field_specification);

61
Altering Tables
 Modifying an existing field:
MODIFY (fieldname new_field_specification);

62
Altering Tables
 Deleting an existing field:
DROP COLUMN fieldname;

63
Deleting Tables
 Syntax to delete table if no table fields
are referenced as foreign keys:
DROP TABLE tablename;
 Syntax to delete table and constraints if
table contains fields that are referenced
as foreign keys:
DROP TABLE tablename CASCADE CONSTRAINTS;

Sql database object

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Sql database object (20)

More from Harry Potter (20)

Recently uploaded (20)

Sql database object