Sql

Structured Query Language (SQL)

1Rushdi Shams, Lecturer, Dept of CSE, KUET, Bangladesh

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Rushdi Shams, Dept of CSE,

KUET

Basics of Table Table is a bucket where you pour data. Data in a specific table is associated with

all other items in that table. In a table, there are basically 3 things-1. Rows / Records / Tuples2. Columns / Attributes / Fields3. Data

3Rushdi Shams, Dept of CSE, KUET

Basics of Table

In the table, the column goes on in a horizontal fashion.

ISBN, AUTHOR, PUBLISHER, TITLE, GENRE, PRINTED are the column names for this table


Basics of Table

In the table, the row goes on in a vertical fashion. Every row in this table has data for ISBN, AUTHOR,

PUBLISHER, TITLE, GENRE, PRINTED


Basic of Table

Books contain relatively disorganized data Organize information using model Resulting in a neatly structured set of rows and

columns

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Relation / Table In relational data model, the table is also called

relation. There are set of rules that are applied on the relations. You must have to know them.

1. A database contains many relations. Every relations in a database must have distinct names

2. Every column in a relation must have distinct names3. Every entries in a column must be in the same domain4. The ordering of columns in a relation is insignificant

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Relation / Table (continued)

5. Duplicate rows are not allowed in a relation

6. The ordering of rows is insignificant7. Multiple values are not allowed in the cells

of a relation8. 2 rows in a relation may contain the same

value for 1 columns but not in all (deviation of 5)

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Terminology The number of rows in a table is called

Cardinality The number of columns in a table is called

Degree

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Languages in Database Systems Data Definition Language (DDL) 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

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Languages in Database Systems Data Modification Language (DML) Used to insert, view, and modify database data

INSERT UPDATE DELETE SELECT

DML commands need to be explicitly saved or rolled back

COMMIT ROLLBACK

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Languages in Database Systems Data Control Language (DCL)

Privileges, Access Control, Administrative Rights

Data Definition Language (DDL)Data Definition Language (DDL)

Rushdi Shams, Lecturer, Dept of CSE, KUET, Bangladesh 12

Creating a table


Creating a table


Dropping a table


DROP TABLE table_name; DROP TABLE cars; DROP TABLE specs; DROP TABLE stock;

Adding a column to a table



Adding columns to a table


Modifying a single column on a table


Modifying columns on a table


Dropping columns on a table


Renaming columns on a table

Data Modification Language (DML)Data Modification Language (DML)


Inserting data into table

REMEMBER- when you are inserting values that are varchar, char or other string types (if any) then you will have to put ‘’ around that value (e.g. ‘value_for_column_X’).


Inserting data into table


Showing data in a table


Updating data in a table


Deleting row from a table


If you do not put WHERE clause, while using it with DELETE statement then all the data in that table will be deleted. SO, BE CAREFUL!

Data Control Language (DCL)Data Control Language (DCL)


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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 objectsControls 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

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Database Objects An Oracle database consists of multiple user

accounts Each user account owns database objects

TablesViewsStored programs

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Oracle Naming Standard Oracle database objects must adhere to the

Oracle Naming Standard1 to 30 characters longMust begin with a characterCan contain characters, numbers, and the

symbols $, _ , and #


Creating New User Accounts Done by DBA Syntax:

CREATE USER username IDENTIFIED BY password;


Trying to access the database As we have created a new user and assigned his

password, should we be able to log into the database with the username and password?

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The Answer


Granting System Privileges Done by DBA Syntax:

GRANT privilege1, privilege2, … TO username;

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So, now can you log in? Yes, you can!


Example Oracle System Privileges

PrivilegePrivilege LevLevelel

PurposePurpose

CREATE SESSIONCREATE SESSION UseUserr

Connecting to databaseConnecting to database

CREATE TABLE CREATE TABLE UseUserr

Creating tables in current user Creating tables in current user schemaschema

UNLIMITED UNLIMITED TABLESPACETABLESPACE

UseUserr

Allows user to create schema Allows user to create schema objects using as much space as objects using as much space as neededneeded

CREATE USERCREATE USER DBDBAA

Creating new usersCreating new users

GRANT ANY GRANT ANY PRIVILEGEPRIVILEGE

DBDBAA

Granting system privileges to Granting system privileges to usersusers

CREATE ANY TABLECREATE ANY TABLE DBDBAA

Creating tables in any user Creating tables in any user schemaschema

DROP ANY TABLEDROP ANY TABLE DBDBAA

Dropping tables in any user Dropping tables in any user schemaschema

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Granting another privilege

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Can you create table yet?


The Reason You have granted your user to create session (log in)

and to create table. But, it is to create on your default SYSTEM database. Therefore, you will have to grant another privilege to your user.

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… & The Solution

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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


Creating a Role Syntax:CREATE ROLE role_name;


Granting Privilege to RoleGRANT privilege1, privilege2, … TO role_name;


Assigning Role to the User Syntax:GRANT role_name TO user_name;


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

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What Happens Next?

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Oracle Data Types Data type: specifies type of data stored in a

field Date, character, number, etc.

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Character Type Data Type VARCHAR2

Variable-length character strings Maximum of 4,000 characters Must specify maximum width allowed Example declaration:student_name VARCHAR2(30)

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Character Type Data Type CHAR

Fixed-length character data Maximum size 2000 characters Must specify maximum width allowed Example declaration:student_gender CHAR(1)

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Character Type Data Type NCHAR

Used for alternate alphabets

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Number Data Type NUMBER

stores values between 10-130 and 10126

General declaration format:variable_name NUMBER(precision, scale)

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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

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Number Data Type Whole number with no digits to right of

decimal point Precision is maximum width Scale is omitted

Sample declaration:s_age NUMBER (2)

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Fixed Point Numbers Contain a specific number of decimal places Precision is maximum width Scale is number of decimal places

Sample declaration:item_price NUMBER(5, 2)

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Floating Point Numbers Contain a variable number of decimal places Precision and scale are omitted

Sample declaration:s_GPA NUMBER

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Date Data Type 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 example: 05-JUN-03

Sample declaration:s_dob DATE

SELECT command


SELECT command


SELECT Command


SELECT Command


SELECT Command


SELECT Command


SELECT Command


SELECT Command


Technology

Sql