SQL ALTER TABLE Keyword

The ALTER TABLE command adds, deletes, or modifies columns in a table. It can also add or delete various constraints in a table.

SQL ALTER TABLE Syntax

For Adding Column:

ALTER TABLE table_name
ADD column_name datatype;

ALTER TABLE table_name

ADD column_name datatype;

For Dropping Column:

ALTER TABLE table_name
DROP COLUMN column_name;

ALTER TABLE table_name

DROP COLUMN column_name;

SQL ALTER TABLE Example – Adding a Column

This query adds an “Email” column to the “Patients” table:

ALTER TABLE Patients
ADD Email VARCHAR(255);

ALTER TABLE Patients

ADD Email VARCHAR(255);

SQL ALTER TABLE Example – Deleting a Column

This query deletes the “Email” column from the “Patients” table:

ALTER TABLE Patients
DROP COLUMN Email;

ALTER TABLE Patients

DROP COLUMN Email;

SQL ALTER TABLE Labs