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In sql you use primary key more than one column in a table
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∙ 11y ago
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Why do you designate one of the candidate key of relation to be the primary key?
We designate one of the candidate key of a relation to be a primary key because that primary key is use for any foreign key references.
What is a primary key what is its purpose and why do you use it?
A primary key is a unique identifier for each record in a database table. Its purpose is to ensure the uniqueness and integrity of the data within the table. It is used to uniquely identify each row, which allows for efficient data retrieval and modification, as well as establishing relationships between tables through foreign keys.
Why do you need the primary key in the database?
without you will not be able to create a relationship
Can super key be as primary key?
I think super key is treated as the primary key because in a table their will be only one primary key.
What are the importance of primary key?
Importance of primary key
Why must the primary key of a parent table be determined before the foreign key in the child table?
Because the foreign key is copied from the primary key of the parent table
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.
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.
Could a table only have one primary key and only one foreign key?
Yes it could. It would have a primary key for its own use and it could then have a foreign linking it to another table. If it is only linked to one other table, then it would only need one foreign key. It is also possible to have the same foreign key linking to more than one table.
What is a primary key of one file that appears in another file?
A primary key is one that uniquely identifies a record . Also there are cases when primary key of one file appears in another file. In that case the key is called Foreign key.
What does the term foreign key mean in databases?
A foreign key is a field in a database table that is used to establish a relationship with another table. It ensures referential integrity by enforcing a link between two tables based on a matching key. This key is typically a primary key in the referenced table.
Is it necessarily that a foreign key is primary key in other table?
It is not mandatory that is must be a primary key but it must be a unique key in the other table.
Why do you designate one of the candidate key of relation to be the primary key?
We designate one of the candidate key of a relation to be a primary key because that primary key is use for any foreign key references.
What the differences between primary key and foreign key?
A primary key is a unique identifier for a record in a table and ensures each record is uniquely identified. A foreign key establishes a relationship between two tables by referencing the primary key in another table. It enforces referential integrity by ensuring that the values in the foreign key column correspond to values in the primary key column of another table.
What is the difference between a primary key and a foreign key?
A primary key uniquely identifies each record in a table and ensures data integrity. A foreign key establishes a relationship between two tables, referencing the primary key of another table to enforce referential integrity.
What is the condition for a key to be a foreign key?
A key is considered a foreign key if it references the primary key of another table to establish a relationship between the two tables. It enforces referential integrity, ensuring that data in the foreign key column corresponds to data in the primary key column.
What ensures the value of the foreign key matches another tables primary key?
It is the DBMS that ensures the value of the foreign key matches another table's primary key when referential integrity constraints are enabled within the DBMS
