Database Slides for DIT students

1. SQL Commands
(Part 3)
By: Ms. Rubab For DIT

2. Delete Statement(DML Statement)
The DELETE Statement in SQL is used to delete existing records from a
table. We can delete a single record or multiple records depending on
the condition we specify in the WHERE clause.
table_name: name of the table
some_condition: condition to choose particular
record.
DELETE FROM table_name WHERE some_condition;
By: Ms. Rubab For DIT

3. DELETE Stataement
We can delete single as well as multiple records
depending on the condition.
The Condition is provided in the WHERE clause.
If we omit the WHERE clause then all the records will be
deleted, and the table will be empty.
By: Ms. Rubab For DIT

4. Sample Table
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
By: Ms. Rubab For DIT

5. Example 1 : Deleting single record:
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
Delete the rows where NAME = ‘Sajid’. This will delete only the
first row.
DELETE FROM Student WHERE NAME = ‘Sajid';
By: Ms. Rubab For DIT

6. Example 1 : Deleting single record(Processing)
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
Delete the rows where NAME = ‘Sajid’. This will delete only the
first row.
DELETE FROM Student WHERE NAME = ‘Sajid';
By: Ms. Rubab For DIT

7. Example 1 : Deleting single record (OUTPUT)
Roll_No Name Address Phone Age
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
Delete the rows where NAME = ‘Sajid’. This will delete only the
first row.
DELETE FROM Student WHERE NAME = ‘Sajid';
By: Ms. Rubab For DIT

8. Example 2: Deleting Multiple records:
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
Delete the rows where Age = ‘17’. This will delete only the first
row.
DELETE FROM Student WHERE Age = ‘17';
By: Ms. Rubab For DIT

9. Example 2: Deleting Multiple
records(Processing)
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
Delete the rows where Age = ‘17’. This will delete only the first
row.
DELETE FROM Student WHERE Age = ‘17';
By: Ms. Rubab For DIT

10. Example 2: Deleting Multiple
records(Output)
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
Delete the rows where Age = ‘17’. This will delete only the first
row.
DELETE FROM Student WHERE Age = ‘17';
By: Ms. Rubab For DIT

11. Delete all the records
There are two
queries to Delete all
the records in a table
Query1: "DELETE FROM Student";
Query2: "DELETE * FROM Student";
OUTPUT: All the records in the table will be deleted, there are no records left to display. The
table Student will become empty!
By: Ms. Rubab For DIT

12. DDL Commands
1. CREATE: This command is used to create the database or its
objects (like tables, database, views, etc) (Details Discussed
in SQL Commands Part 1)
2. DROP: This command is used to delete objects from the
database.
3. ALTER: This is used to alter the structure of the database.
4. TRUNCATE: This is used to remove all records from a table,
including all spaces allocated for the records are removed.
5. RENAME: This is used to rename an object existing in the
database.
By: Ms. Rubab For DIT

13. SQL | DROP
DROP is used to delete a whole database or just a table.The DROP
statement destroys the objects like an existing database, table, index,
or view.
A DROP statement in SQL removes a component from a relational
database management system (RDBMS).
Syntax:
DROP object object_name
By: Ms. Rubab For DIT

14. Drop Syntax: Examples:
1.
DROP TABLE table_name;
table_name: Name of the table to be deleted.
2.
DROP DATABASE database_name;
database_name: Name of the database to be deleted.
The DROP command works for a single table, multiple tables or
the entire database
By: Ms. Rubab For DIT

15. SQL | Truncate
The result of this operation quickly removes all data from a table
It is faster than DELETE as DELETE removes the data row by row.
Syntax:
TRUNCATE TABLE table_name;
table_name: Name of the table to be truncated.
By: Ms. Rubab For DIT

16. DELETE DROP TRUNCATE
DML Command
Deletes the rows of a table, could
be a single row , multiple rows or
all the rows of a table, based on
the clause.
DELETE Deletes only the Data not
the structure of the Table
Rollback is possible before commit
DDL Command
DROP Deletes the entire schema/
structure (Which means the
contents as well as name and
constraints)
DDL Command
It also deletes the rows of a Table.
It doesn’t allow single Row
Deletion as it doesn’t support
WHERE Clause
Rollback is not possible
Rollback creates a temporary log of the data in the database that helps in data recovery before commit statement
DELETE VS DROP VS TRUNCTAE
By: Ms. Rubab For DIT

17. SQL | ALTER
ALTER TABLE is used to add, delete/drop or modify columns in
the existing table. It is also used to add and drop various
constraints on the existing table.
3 Types of
ALTERS
ADD DELETE/DROP Modify
By: Ms. Rubab For DIT

18. ALTER TABLE – ADD
ADD is used to add columns into the existing table. Sometimes
we may require to add additional information, in that case we do
not require to create the whole database again, ADD comes to
our rescue.
Syntax:
ALTER TABLE table_name ADD (Columnname_1 datatype,
Columnname_2 datatype, … Columnname_n datatype);
table_name: Name of the table to be altered
Columnname: Name of the Columns to be added
Datatype: Type of Data to be supported by new column
By: Ms. Rubab For DIT

19. ALTER TABLE – DROP
DROP COLUMN is used to drop column in a table. Deleting the unwanted
columns from the table.
Syntax:
ALTER TABLE table_name DROP COLUMN column_name;
By: Ms. Rubab For DIT

20. ALTER TABLE-MODIFY
It is used to modify the existing columns in a table. Multiple
columns can also be modified at once.
ALTER TABLE table_name
ALTER COLUMN column_name column_type;
Example:
ALTER TABLE Student
MODIFY COURSE varchar(20);
By: Ms. Rubab For DIT

21. SQL | ALTER (RENAME)
Sometimes we may want to rename our table to give it a more
relevant name. For this purpose we can use ALTER TABLE to
rename the name of table.
Syntax(MySQL):
ALTER TABLE table_name RENAME TO new_table_name;
Columns can be also be given new name with the use of ALTER
TABLE.
Syntax(MySQL):
ALTER TABLE `students` CHANGE
`old_name` `new_name` datatype(size);
By: Ms. Rubab For DIT

22. Sample Table
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
Table Name: DATA
By: Ms. Rubab For DIT

23. Re-naming Table:
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
ALTER TABLE DATA RENAME TO Students;
TABLE NAME: Students
By: Ms. Rubab For DIT

24. Re-naming columns:
Roll_No Name Address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
ALTER TABLE Students RENAME Column Name TO
std_name,Address TO std_address;
TABLE NAME: Students
By: Ms. Rubab For DIT

25. Re-naming columns:
Roll_No std_name std_address Phone Age
1 Sajid Sobhodero Xxxxxxxxxxx 18
2 Majid Ranipur Xxxxxxxxxxx 18
3 Abid Hinjorja Xxxxxxxxxxx 18
4 Zahid Sajiyoon Xxxxxxxxxxx 17
5 Anwar Niwaro Xxxxxxxxxxx 17
6 Ghulam Nabi Razal Memon Xxxxxxxxxxx` 18
ALTER TABLE Students RENAME Column Name TO
std_name,Address TO std_address;
TABLE NAME: Students
By: Ms. Rubab For DIT