/* The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only ONE primary key; and in the ...

In mysql, the primary key constraint is used to uniquely identify each record in a table.primary key contains unique values only and the column defined as primary key column can not be null. a table ...

-- Primary keys must contain UNIQUE values, and cannot contain NULL values. -- A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns ...

Note that the "P_Id" column in the "Orders" table points to the "P_Id" column in the "Persons" table. In MySQL, the FOREIGN KEY on one table is used to point a PRIMARY KEY in another table. We have ...

Duplicate and Ignore on MySQL Inserts. MySQL table primary keys and unique indexes prevent multiple rows with the same index from being added to the table.