Implementation of Alter query in sql

Question

Implementation of Alter Query

Answer 1

SQL Alter Query 

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.

syntax : ALTER TABLE table_name  ADD (Columnname_1  datatype, Columnname_2  datatype,…Columnname_n  datatype);

• ALTER Table - DROP :

syntax : ALTER TABLE table_name DROP COLUMN column_name;

Example :  

roll no	name	class	address	marks
1	Aman	2	GOA	100
2	Ankita	3	DELHI	99
3	Ananya	4	BHUTAN	98
4	Atul	5	SIKAR	100

ALTER TABLE school DROP COLUMN address;

Output : 

roll no	name	class	marks
1	Aman	2	100
2	Ankita	3	99
3	Ananya	4	98
4	Atul	5	100

• ALTER Table - MODIFY :

syntax : ALTER TABLE table_name MODIFY column_name column_type;

Example : 

ALTER TABLE school ADD (AGE number(3),Subject varchar(20));

Output : 

roll no	name	class	marks	AGE	Subject
1	Aman	2	100
2	Ankita	3	99
3	Ananya	4	98
4	Atul	5	100

ALTER TABLE school ADD (AGE number(3),Subject varchar(40));

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