The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.
ALTER TABLE table_name
ADD column_name datatype;	to add column
	to delete column
ALTER TABLE table_name
DROP COLUMN column_name;
ALTER TABLE Customers
DROP COLUMN Email;

HOW TO ADD ONE COLUMN
ALTER TABLE `foods` ADD `HTML` VARCHAR(200) NOT NULL AFTER `type`;

to modify the datatyoe

ALTER TABLE Persons

MODIFY Age int NOT NULL;

ALTER TABLE Persons

ADD CHECK (Age>=18);

ALTER TABLE Persons

DROP CHECK CHK_PersonAge; ALTER TABLE Persons modify ADD CONSTRAINT df_City DEFAULT 'Sandnes' FOR City; ALTER TABLE Persons ADD CONSTRAINT df_City DEFAULT 'Sandnes' FOR City;