Primary Keys : PRIMARY KEY « Table « MySQL Tutorial

MySQL Tutorial

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MySQL Tutorial » Table » PRIMARY KEY

4. 15. 1. Primary Keys

A primary key data must be unique.

Only one primary key can exist for each table.

A primary key values can never be null.

MySQL requires you to specify NOT NULL when creating a table with a given column specified as PRIMARY KEY.

4. 15. PRIMARY KEY
	4. 15. 1.	Primary Keys
	4. 15. 2.	Create primary key in column definition
	4. 15. 3.	Create primary key after column definition
	4. 15. 4.	Multiple-Column Primary Keys
	4. 15. 5.	Auto_INCREMENT primary key
	4. 15. 6.	Use two columns as the combined primary key
	4. 15. 7.	Use partial indexing as the primary key
	4. 15. 8.	ALTER TABLE table_name ADD PRIMARY KEY index_name (column_name[,...]);
	4. 15. 9.	To drop a PRIMARY KEY
	4. 15. 10.	To remove a primary key
	4. 15. 11.	Alter table to drop primary key and foreign key
	4. 15. 12.	Add Index and primary key to a table in table creation command

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