Question

80.Which of the following is not true for Primary key?

1. A primary key uniquely identifies records.
2. A table can have only one primary key.
3. A primarykey field can be NULL.
4. None of these​

Answer 1

Answer:

sir

Explanation:

2.A table can have only one primary key.

Answer 2

A table can have only one primary key.

Also known as the first keyword, it is the key to a related website that is unique to all records. It is a completely different identifier, which includes the motive force license, the smartphone quantity, or the automobile identity quantity (VIN).

A related website should usually have one key and one hand. The first number key is the column - or set of columns - in the table that specifically identifies the rows on that desk.

For example, within the desk below, Cha Customer-Cha, which displays the ID number assigned to specific customers, is the first key. CUSTOMERS. Customer No. Name.