SQL Interview Questions


Structured Query Language (SQL)

It is a programming language, which is domain specific. It is used for handling the data, which is stored in relational database management system. It manages the structured data in which relations are present among the distinct variables of the data. Moreover, database administrators or DBA take the help of special softwares for the organization or storage of data.

In SQL, the users can ingress several records of data with the help of specific SQL commands. Along with this, the users do not need to specify the criteria for reaching a record. The applications which are data driven in SQL can be attacked by SQL injection. The SQL injection inserts foul statements into a field for carrying out the task.  

Furthermore, PostgreSQL is an object relational system of database, which increases the efficiency of SQL. It can store and retrieve huge amount of workloads. Along with this, TSQL adds many characteristics to SQL. Moreover, AQL is similar to SQL with some differences, which can be located in the AQL chart.

 The commands in SQL

The SQL queries calls data from the database. In order to retrieve the data and solve the SQL queries, SQL commands are used. The SQL commands are classified into four classes.

  • DDL or Data Definition Language: DDL is used to define the design of database.
    • Create- creates functions, index, tables, etc. SQL create table is used to create table.
    • Drop- deletes objects
    • Alter- modify the makeup of the SQL database
    • Truncate- deletes records from the collection of data
    • Comment- adds comments
    • Rename- rename an object
  • DML or Data manipulation Language: DDL is used to change modify the data of the database.
    • Select- recalls data
    • Insert- inserts data
    • Update- updates the data
    • Delete- deletes records
  • DCL or Data control language: deals with the controls of the collection of data.
    • Grant- grants the user access to the database.
    • Revoke- takes back the user’s access o the database.
  • TCL or Transaction Control Language: TCL deals with transactions in the database.
    • Commit: makes a transaction
    • Rollback: Rollback SQL abates a transaction
    • SavePoint- establishes a savepoint in the transaction
    • Transaction- specifies transaction’s characteristics


Online web assistance

The W3schools sql is an online tutorial site, which helps the users to learn SQL online and it offers sql queries for practice The users can do SQL practice online with the help of SQL queries for practice, which are present on the site. W3schools sql contains several SQL questions and SQL MCQ, which helps the users to prepare for SQL interview questions and SQL queries for interview.

The site contains SQl interview questions for testers, SQL interview questions for freshers, and SQL interview questions for experienced. The several SQL online test and SQL quiz conducted on the site helps the users to prepare with the SQL interview questions and answers. The users can prepare for the basic SQL interview questions, SQL joins interview questions, and SQL developer interview questions with the help of SQL query interview questions and answers provided on the site. The SQL queries interview questions are also solved on the site.

 Speed up your work

There are several online assistance, which help the users with their databases and speed up their works.

  • SQL index: The SQL Index makes the process of performing the queries fast. The SQL online index speeds up the procedure of SQL programming.
  • Online SQL compiler: It is used to compile the SQL database online.
  • SQL editor: The online SQL editor provides and efficient method of querying and managing the databases.
  • SQL beautifiers: SQL formatter garnishes the SQL commands instantly and change codes into well-arranged script. It beautifies the SQL view of the database.

 

Triggers in SQL

Triggers in SQL are objects of the databases which come into action whenever an event is occurring. They are a distinct type of stored procedure in SQL.Triggers in SQL are of two types

  • DDL trigger: They come into action whenever an event of DDL command occurs.
  • DML trigger: They come into action whenever an event of DML command occurs.


Some clauses in SQL

  • For  Grouping data: In SQL group by clause is used for grouping similar information into groups by using functions such as AVG, COUNT, SUM, MIN, and MAX.
  • For converting: SQL convert changes an expression of a specific data type to the other.
  • Not in: SQL not in is used to call a column with does not contain any entry in the table.

 
NoSQL and MySQL

NoSQL database is a procedure for saving and retrieving information, which is not in tabular form. The structure of data in NoSQL db can be graph, columns or documents. It is more flexible than RDBMS and therefore, is used in actual time web applications and when the size of data is big.

MySQL is a RDBMS, which is open source. It is a part of LAMP and is used in C and C++. My SQL stores data in tabular structure. phpMyAdmin is an efficient management equipment for MySQL.

The users can get SQL download and SQL tutorial from W3schools. Also, Nosql tutorial, and PL SQL tutorial is available on the site.

 NoSQL vs SQL

Some of the differences between NoSQL and SQL are given below.

  • SQL deals with tabular data whereas; NoSQL deals with graphs and documents.
  • SQL databases use SQL and focuses on defining and changing the data, and NoSQL concentrates on the collection of files.
  • SQl can handle complex queries, whereas, NoSQL cannot.
  • SQL databases focuses on ACID properties and, NoSQL databases go in accordance with the Brewers CAP theorem.
  • SQL databases do not store hierarchical data. On the contrary, NoSQL stores hierarchical data.  

Some of the many SQL Interview Questions listed below will help you get an idea about what questions gets asked in such jobs related to Software Engineering & Tech. Get through the SQL Interview bar with our selected SQL Interview Questions for all SQL enthusiasts!


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