Define composite key

Define composite key.

- A key formed by combining at least two or more columns.
- It is a combination of two or more columns in a table that can be uniquely identify each row in the table.
- A composite key can be defined as the primary key.
- It is a special type of candidate key that is only formed by a combination of two or more columns.
Define default constraint
Default constraint is used to fill column with default value defined during creation of table if nothing is supplied while inserting data........
What is a transaction and what are ACID properties?
Transaction encapsulates SQL commands and work as a single unit........
Different isolation levels defined in SQL Sever
Isolation levels determine the degree of isolation of data during concurrent access.......
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