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A primary key is a column which uniquely identifies the records in a table. In a broad sense, a primary key is the mixture of a unique key and an index: A collumn with a primary key is indexed to deliver a faster query, and doesn't allow duplicate values to ensure specific data. Most programmers recommend all tables having a primary key (and only one) to enhance the speed of queries and overall database performance. An example of a primary key may be found in a table named "departments," which might have a collumn named "department_number" that uniquely identifies each department in the table with a number. ---- A foreign key is a column (the child collumn) in a table which has a corresponding relationship and a dependency on another collumn (the parent collumn) that is usually in a different table. Parent collumns can have multiple child collumns, but a child collumn can only have one parent collumn. The child collumn is the collumn with the foreign key; the parent collumn does not have the foreign key "set" on it, but most databases require the parent collumn to be indexed. Foreign keys are made to link data across multiple tables. A child collumn cannot have a record that its parent collumn does not have. Say a table named "employees" has 20 employees (rows) in it. There are 4 departments in the "departments" table. All 20 employees must belong to a department, so a collumn in the "employees" table named "department" would point to the primary key in the "departments" table using a foreign key. Now all employees must belong to a department as specified by the "departments" table. If a department isn't specified in the "departments" table, the employee cannot be assigned to it.
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What are the basic components of a database?
Tables, Entities, Attributes, Primary Keys, and Foreign Keys
What the differences between primary key and foreign key?
A primary key is a special case of unique keys which doesnt accept duplicates. The difference between unique keys is that "NOT NULL" constraint is not automatically enforced, while for primary keys it is mandatoryUnique keys and primary keys can be referenced by foreign keys
How functional dependency is related to database table design?
The functional dependency is related to the database table design through the foreign and primary keys. The foreign and primary keys are functionally dependent on each other.
Can a primary key be a foreign key?
Yes, a primary key can also be a foreign key. This is known as a composite key, where one or more columns in a table are both primary keys for that table and also act as foreign keys linking to another table.
How much types of keys are available in dbms?
There are five types of keys in database management system . The name of the five keys are as follows .:1) surrogate key -which is the system generated primary key .2) Primary key - same function as surrogate key but user defined.3) candidate key -combination of two more keys.4) alternate keys - alternative for candidate keys.5) foreign key - primary key of another table.There are five types of keys in database management system.These five keys are surrogate, primary, candidate, alternate, foreign keys .
Explain the concept of foreign key How a foreign key differs from a primary key?
Foreign keys are used to link one database with another. A primary key is an attribute of a record that allows users to identify information.
Types of keys?
There are many keys in database each having particular use. Types of keys in database are : Primary key, candidate key, alternate key, foreign key, surrogate key.
When was Foreign Keys created?
Foreign Keys was created in 1985.
How do foreign keys ofrelations relate to candidate keys?
Foreign keys and candidate keys serve distinct roles in relational databases. A candidate key is a set of one or more attributes that can uniquely identify a tuple within a relation, while a foreign key is an attribute or a set of attributes in one relation that refers to the primary key of another relation. Foreign keys establish relationships between tables, ensuring referential integrity, whereas candidate keys ensure that each row within a table can be uniquely identified. Thus, while foreign keys link tables, candidate keys define uniqueness within a table.
How do you identify the primary key and the foreign keys?
The primary key is identified as a unique identifier for a table, ensuring that no two records have the same value in that column or set of columns. It is typically defined during the table design phase and can be a single column or a combination of columns. Foreign keys, on the other hand, are fields in a table that create a link between that table and another table; they reference the primary key of another table to establish a relationship. To identify foreign keys, look for columns that are intended to reference the primary key of another table, often indicated by naming conventions or constraints defined in the database schema.
What is the relationship between tables in library management system?
In a library management system, tables represent different entities such as books, users, transactions, etc. The relationship between these tables is established through keys like primary keys and foreign keys. For example, the books table may have a primary key "book_id" which is referenced as a foreign key in the transactions table to link books with users.
Do Primary keys have to be numbers that are entered by the user?
Primary keys have to be numbers that are entered by the user.
