Why you need primary key?

Answer 1

The primary key of a table uniquely identifies each row in the table. It may also serve as a foreign key to other related tables. For example, a Customer table would use a CustomerID field (typically an autogenerated sequential integer) to uniquely identify each row in the table. This value would also appear in an Orders table as a foreign key to associate that customer with an order. Although unique individual values are best for primary keys, they may also be "compound" keys, that is, made up of two or more values in each row. For example, a table containing airline flight data might use a compound key of the flight number and the destination to uniquely identify the row.

Answer 2

Primary key concept is used in database while storing the records. the main aim of this is to identify the tuples(or records) stored in the table uniquely. when you make any of the attribute as a primay key, you cant have duplicate values for it. it should always have unique values, thus helping us to distinguish between records when we need a uniqueness in our database then we used a primery key.primery key is a field or group of value that shows the uniqueness in the database.it cannot be duplicate or null value.

Answer 3

Whenever accessing or editing data it is important that you can ensure the correct data is being accessed. Primary keys allow you to select, update or delete a specific row with no risk of that action having impacts on data other than the row with that key id. This effect can be accomplished with a multiple column unique constraint, but these operations are slower and require significally larger indexes than a primary key.

Answer 4

In relational database design, a unique key or primary key is a candidate key to uniquely identify each row in a table. A unique key or primary key comprises a single column or set of columns. No two distinct rows in a table can have the same value (or combination of values) in those columns. Depending on its design, a table may have arbitrarily many unique keys but at most one primary key. A unique key must uniquely identify all possible rows that exist in a table and not only the currently existing rows. Examples of unique keys are Social Security numbers (associated with a specific person) or ISBNs (associated with a specific book). Telephone books and dictionaries cannot use names or words or Dewey Decimal system numbers as candidate keys because they do not uniquely identify telephone numbers or words. A primary key is a special case of unique keys. The major difference is that for unique keys the implicit NOT NULL constraint is not automatically enforced, while for primary keys it is. Thus, the values in a unique key columns may or may not be NULL. Another difference is that primary keys must be defined using another syntax.

Answer 5

Primary key is used to avoid redundancy in the database.

Answer 6

it is the zipcode + house number of your record, a unique identifier.

Answer 7

The importance of a primary key is that it is a single attribute which can uniquely identifies an instance of an entity.