# More On Alter Table

# [Lecture] Add and Remove Primary Key

-- Add Primary Key to a Table
ALTER TABLE <TABLE_NAME>;
ADD PRIMARY KEY (<COLUMN_NAME>);

-- Remove Primary Key from a Table
ALTER TABLE <TABLE_NAME>;
DROP PRIMARY KEY;

# [Lecture] Add and Remove Foreign Key

-- Add Foreign Key to a Table
ALTER TABLE <TABLE_NAME>
ADD CONSTRAINT <CONSTRAINT_NAME>
FOREIGN KEY (<COLUMN_NAME>) REFERENCES <TABLE_NAME>(<COLUMN_NAME>);

-- Remove Foreign Key from a Table
ALTER TABLE <TABLE_NAME>
DROP FOREIGN KEY <CONSTRAINT_NAME>;

# [Lecture] Add Unique Constraint

-- How to Add a Unique Constraint to a Column
ALTER TABLE <TABLE_NAME>
ADD CONSTRAINT <CONSTRAINT_NAME> UNIQUE (<COLUMN_NAME>);

-- How to Remove a Unique Constraint from a Column
ALTER TABLE <TABLE_NAME>
DROP INDEX <CONSTRAINT_NAME>;

# [Lecture] Change Column Name

ALTER TABLE <TABLE_NAME> CHANGE `OLD_COLUMN_NAME` `NEW_COLUMN_NAME` <DATA_TYPE>;

# [Lecture] Change Column Data Type

ALTER TABLE <TABLE_NAME> MODIFY <COLUMN_NAME> <DATA_TYPE>;

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