Post #2049

Data Analytics Interview Questions with Answers 1. What are Query and Query language? A query is nothing but a request sent to a database to retrieve data or information. The required data can be retrieved from a table or many tables in the database. Query languages use various types of queries to retrieve data from databases. SQL, Datalog, and AQL are a few examples of query languages; however, SQL is known to be the widely used query language. 2. What are Superkey and candidate key? A super key may be a single or a combination of keys that help to identify a record in a table. Know that Super keys can have one or more attributes, even though all the attributes are not necessary to identify the records. A candidate key is the subset of Superkey, which can have one or more than one attributes to identify records in a table. Unlike Superkey, all the attributes of the candidate key must be helpful to identify the records. 3. What do you mean by buffer pool and mention its benefits? A buffer pool in SQL is also known as a buffer cache. All the resources can store their cached data pages in a buffer pool. The size of the buffer pool can be defined during the configuration of an instance of SQL Server. The following are the benefits of a buffer pool: Increase in I/O performance Reduction in I/O latency Increase in transaction throughput Increase in reading performance 4. What is the difference between Zero and NULL values in SQL? When a field in a column doesn’t have any value, it is said to be having a NULL value. Simply put, NULL is the blank field in a table. It can be considered as an unassigned, unknown, or unavailable value. On the contrary, zero is a number, and it is an available, assigned, and known value.