Super key in database can be defined as the combination of fields which can be used to uniquely identify a row present in a table. A unique super key is used for each and every row present in a RDBMS table. At least one field in a superkey must have value while the rest can […]
What is Secondary Key?
The questions about secondary key in SQL is common in most database interviews. The Candidate keys which are not selected as primary key is classified as Secondary key. Consider that you have a table, there will be several keys in a table which can be selected as a primary key. The keys which has the […]
What is Natural Key?
Natural key can be defined as an identifier of row which is composed of data. The data present in the database will describe according to its attributes. The row identifier in a database is the focal point of clustered and nonclustered indexes. What is Cost Based Optimizer? Why it is called as Natural key? Consider […]
What is Meant by Key in SQL?
Key in SQL can be defined as the subset of the columns present in tables which permit to uniquely identify a row. Every row in a table will have unique value for key. Keys are used to fetch records from a table according to the given condition. The different types of key used to retrieve […]