SQL ADD COLUMN

The ADD COLUMN statement in SQL is used to add new columns to an existing table.

Key Features of SQL ADD COLUMN

• Adds a new column without affecting existing data.
• Can specify data type, default value, and constraints.
• Multiple columns can be added in a single statement.

SQL ADD COLUMN Syntax

ALTER TABLE table_name 
ADD column_name datatype constraint;

Example: Adding a Single Column

ALTER TABLE Employees 
ADD Email VARCHAR(100);

• Adds a new column Email to the Employees table.

Example: Adding Multiple Columns

ALTER TABLE Employees 
ADD (Age INT, Address VARCHAR(255));

• Adds Age and Address columns to the Employees table.

Example: Adding a Column with Default Value

ALTER TABLE Employees 
ADD Status VARCHAR(10) DEFAULT 'Active';

• Adds a Status column with a default value of 'Active'.

Example: Adding a Column with NOT NULL Constraint

ALTER TABLE Employees 
ADD JoinDate DATE NOT NULL;

• Adds a JoinDate column that cannot have NULL values.

Summary

• ADD COLUMN allows modifying an existing table.
• Supports constraints like DEFAULT, NOT NULL, etc.
• Multiple columns can be added at once.
• Ensure existing data compatibility before adding columns.