What is primary key and foreign key with example?

Question

1. A primary key is used to ensure data in the specific column is unique. A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables. 2. It uniquely identifies a record in the relational database table. 28 мар. 2020 г.

What is primary key and example?

A primary key is a column -- or a group of columns -- in a table that uniquely identifies the rows in that table. For example, in the table below, CustomerNo, which displays the ID number assigned to different customers, is the primary key. CUSTOMERS. CustomerNo.

What are three examples of primary key?

A primary key, also called a primary keyword, is a key in a relational database that is unique for each record. It is a unique identifier, such as a driver license number, telephone number (including area code), or vehicle identification number (VIN). A relational database must always have one and only one primary key.

What is a good example of a primary key?

For example, students are routinely assigned unique identification (ID) numbers, and all U.S. citizens have government-assigned and uniquely identifiable Social Security numbers. Street addresses or driver license numbers are examples of primary keys used to uniquely identify (respectively) locations or cars.

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