An introduction to SQL and in details discussion on DDL commands with syntax as well as examples.

1. SQL Fundamentals
Oracle 11g
M U H A M M A D WA H E E D
O R AC L E D ATA BA S E D E V E LO P E R
E M A I L : m .wa h e e d 3 6 6 8 @ g m a i l . co m
.
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Lecture#1

2. What is SQL?
•Structured Query language (SQL) pronounced as "S-Q-L" or sometimes
as "See- Quel”( interrogate)
•It is language for operating Databases.
•It can be effectively used to insert, search, update, delete records
optimizing and maintenance of databases.
•Mostly databases use SQL like MySQL Database, Oracle, MS SQL server,
Sybase etc.
• How to use SQL syntaxes?
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3. Writing SQL Statements
•SQL statements are not case-sensitive. But we will use
UPPERCASE letters for syntax and lowercase for user-defined
data.
•SQL statements can be on one or more lines.
•Keywords cannot be abbreviated or split across lines.
•Clauses are usually placed on separate lines.
•Indents are used to enhance readability.
•In iSQL*Plus, SQL statements can optionally be terminated
by a semicolon(;).
•In SQL*Plus, you are required to end each SQL statement
with a semicolon(;).
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4. Naming conventions of SQL
(General)
•Name will be unique and does not exist as a reserved/keyword.
•Can have maximum of 30 characters.
•Use letters, numbers & underscores ( _ ) in names.
•Names must begin with a letter and not end with ( _ ).
•Avoid consecutive underscores. e.g. first__name
•Use underscores instead of space.
•Names should be meaningful.
•If you have to use abbreviation make sure they are commonly
understood.
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5. SQL statements
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6. Connect DBMS
•There are different user categories due to security/access
control.
•Database Administrators
•Application Developers
•Application Administrators
•Database Users
•Here is the link to Oracle’s site for detailed knowledge on
user types and their roles:
https://docs.oracle.com/cd/B28359_01/server.111/b28310/
dba001.htm#ADMIN11013
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7. Database Users(Administrator)
•In addition to the user accounts that you create,
the database includes several user accounts that
are automatically created upon installation.
•In addition to the user accounts that you create,
the database includes several user accounts that
are automatically created upon installation.
•All databases include the administrative accounts
SYS, SYSTEM, SYSMAN.
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8. Create new user/database
•There are following steps for creating:
•SQL>CREATE USER <username> IDENTIFIED
BY <password>
•SQL>GRANT DBA TO <username>
•SQL>COMMIT;
•SQL>EXIT;
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9. Current User
•Here is the command to check which user is currently
logged in.
•SQL> SHOW USER
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10. Tables/Relations/Entities
•Let we have a small database named as uaar which deals with student,
department ,subject and teacher.
•We will perform all of our operations depending upon the defined
structure as below:
•Student (std_id , std_name , std_dept_id, d_o_b , age)
•Teacher (tch_id ,tch_name , tch_qualification)
•Department (dept_id , dept_name)
•Subject (sub_id , sub_title , credit_hour)
•Result (exam_id, sub_id, tch_id , total_marks , exam_date)
•Sub_result (exam_id , std_id , obt_marks , percentage )
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11. ERD of UAAR
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12. Data Definition
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13. Create Table
•We use SQL statement for creating/defining new table with
“CREATE”keyword and following syntax:
•SQL> CREATE TABLE <table_name>
•( <column_name> <data_type>,
•<column_name> <data_type>,
•<column_name> <data_type> );
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14. Alter Table
•In case, you have some new data definition to add or want to
edit/delete existing data definitions use this SQL command with
keyword “ALTER” and following syntax:
•SQL> ALTER TABLE <table_name>
ADD <column_name> <data_type>;
•SQL> ALTER TABLE <table_name>
DROP COLUMN <column_name>;
•SQL> ALTER TABLE <table_name>
MODIFY COLUMN <column_name> <data_type>;
•*Note: Some database systems don’t allow to drop a column.
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15. Rename Table
•The RENAME statement is used to assign a new name to the existing
table.
•Rename statement has following syntax:
•SQL> ALTER TABLE <table_name>
RENAME TO <new_table_name>;
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16. Drop/Delete Table
•The DROP statement is used to delete a table along with table
structure,attributes and data.
•Drop statement has following syntax:
•SQL> DROP <table_name>;
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17. Truncate Table
•The TRUNCATE statement is used to delete all data in a table . It does
not delete table structure or attributes.
•TRUNCATE statement has following syntax:
•SQL> TRUNCATE <table_name>;
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18. COMMENTS
•Use the COMMENT statement to add to the data dictionary a comment
about a table or table column etc.
•We use following syntax for creating comments:
•COMMENT ON COLUMN <column_name>
IS ‘<comment_statement>';
•We use following syntax to remove comments:
•COMMENT ON COLUMN <column_name> IS ' ';
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19. Your Suggestions?
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