13 Best Interview Questions in SQL.

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SQL short form for Structured Query Language is a type of domain specific programming language used for managing the data in Database Management Systems(DBMS). SQL programming skills are highly wanted and essential in the market, as there is an immense use of Database Management Systems (DBMS) in almost every software application. In order to get a good job, candidates need to crack the base interview in which they are asked countless interview questions in SQL.

Following are some of the most asked interview questions in SQL, and

which are likely to be asked to you during the SQL interview. Candidates are very likely to be asked basic SQL interview questions to advance level SQL questions reliant on their experience and various other factors. 

Read- Interview questions of Wipro

What do mean by DBMS?

A Database Management System (DBMS) is a program that controls construction, maintenance and usage of a database. DBMS can be also called as File Manager that manages data in a database other than saving it in our file systems.

What do you mean by RDBMS?

RDBMS or Relational Database Management System. RDBMS is used to store the data into the collection of tables, which is associated by common fields between the columns of the table. RDBMS also provides relational operators to operate the data stored into the tables. Eg. SQL

What is meant by SQL?

SQL or Structured Query Language , is used to communicate with the Database. This is a very standard language used to perform various tasks such as retrieval, updation, insertion and deletion of data from a different database. The Standard SQL Commands are  the Select.

What is meant by Database?

Database is nothing but a very organized form of data for easier access, storing, retrieval and managing of this data. Database is also referred as a structured form of data which can be easily accessed in many ways. Eg. : School Management Database.

Define tables and Fields?

A table is defined as a set of data that can be organized in a model in form of Columns and Rows. Columns can be characterized as vertical, and Rows as horizontal. A table has to be specified with number of columns called fields but you can have any number of rows which is called record.

Define normalization?

Normalization is called as the process of minimizing redundancy and the dependency by organizing various fields and table of a database. The main use of Normalization is to add, delete or modify field that can be made use in a single table.

Define  Denormalization.

Denormalization is defined as a technique used to access the data from higher to lower normal forms of database. Denormalization is also known as the process of introducing redundancy into a table by combining data from the other related tables.

Explain a Cursor?

A database Cursor is used as a control which helps in enabling traversal over the rows or records in the table. This can be regarded as a pointer to one row in a set of rows. Cursor is very useful for traversing such as retrieval, addition and removal of multiple database records.

Define a trigger?

A Database trigger is a code or program that automatically gets executed with help of some response to some event on a table in a database. Mostly, trigger helps in maintaining the integrity of the original database.

What is meant by Datawarehouse?

Datawarehouse is a main repository of data from multiple sources of information. Those data are consolidated, transformed and made available for the data mining and online processing. Warehouse data usually have a subset of data known as Data Marts.

What do you mean by the following Union, minus and Interact commands?

UNION operator is used to merge the results of two tables, and it also eliminates any duplicate rows from the tables. MINUS operator is used to return rows from the first query but not also from the second query. Matching records of first and second query and other rows from the first query are displayed as a final result set. INTERSECT operator is used to return rows returned by both the first and second queries.

Define CLAUSE?

Clause in SQL is defined as the limit of the result set by providing condition to the query. This usually extracts some rows from the whole set of records. Eg. – Query that has WHERE condition

What is meant by aggregate and scalar functions?

Aggregate functions are used to calculate mathematical calculation and return every one of the single values. These can be used to calculate from the columns in a table. Scalar functions also return a single value based on the very input value. Eg.: Aggregate – max(), count – Calculated with respect to given numeric. Scalar – UCASE(), NOW() – Calculated with respect to given strings.