My Sql syntax and Examples.

1.) How to insert a column in table?
→   Syntax: Alter table <Table Name> add <Column Name Datatype(size)>;
→   Example: Alter table Student add Address varchar(20);

2.) How to insert multiple columns in table?
→   Syntax: Alter table <Table Name> add <Column Name Datatype(size), Column Name Datatype(size), Column Name Datatype(size)>;
→   Example: Alter table Student add (Col1 varchar(2), col2 number(5), col3 number(8));

3.) How to drop the specific column?
→   Syntax : Alter table <Table Name> drop column <Column Name>;
→   Example:  Alter table Student drop column Address;

4.) How to drop the one or more column at a time?
→   Syntax : Alter table <Table Name> drop column <Column Name, Column Name>;
→   Example: Alter table Student drop column (col1, col2, col3, ......, col_n);

5.) How to rename the column?
→   Syntax : Alter table <Table Name> rename column <Old Column Name> to <New Column Name>;
→   Example: Alter table Student rename column Phone to Phone_Number;
 
6.) How to change or modify the datatype of single variable?
→   Syntax : Alter table <Table Name> modify <Column Name Datatype(Size)>;
→   Example: Alter table Student modify Name varchar(30);
 
7.) How to change or modify the datatype of multiple variables?
→   Syntax : Alter table <Table Name> modify <Column Name Datatype(Size), Column Name Datatype(Size)>;
→   Example: Alter table Student modify <Name varchar(30), Roll number(7)>;