Top 100+ Advanced SQL Interview Questions 2020-2021 - 1

Question: 1

What is DML?

It is a special language used to manipulate the Data. Data Manipulation Language (DML), which is used to select, insert, update, and delete data in the objects defined using DDL.

Question: 2

What is a trigger?

• Triggers are a special type of stored procedure, which gets invoked upon a certain event.
• They can be performed upon an INSERT, UPDATE and DELETE.

Question: 3

What are the conditions to achieve the normalization?

There are few conditions to achieve the normalization:

• There should be a unique row identifier.
• A table should store only data for a single type of entity. For e.g. details for book’s publisher and book’s author should be saved under different table.
• A table should avoid columns which can be null-able.
• A table should avoid duplication of data and columns.

Question: 4

What is index?

• INDEX is a general term for an SQL feature used primarily to speed up execution and impose UNIQUENESS upon data.
• You can use an index to gain fast access to specific information in a database table.
• An index is a structure that orders the values of one or more columns in a database table.
• The index provides pointers to the data values stored in specified columns of the table, and then orders those pointers according to the sort order you specify.

Question: 5

What is a foreign key?

A FOREIGN KEY is one or more columns whose values are based on the PRIMARY or CANDITATE KEY values from the database.