Frequently Asked SQL Interview Questions
SQL is a must-have skill because the Relational Database Management System (RDBMS) is the most widely utilized database in businesses. This blog on SQL Interview Questions and Answers seeks to walk you through a variety of SQL questions based on concepts like MS SQL Server and MySQL databases. This is a one-stop shop where you can get the most bang for your buck and conveniently prepare for job interviews. Here, check more pl/sql interview questions.
This blog post is about SQL Interview. The following three categories of questions and replies can be identified:
SQL stands for 'Structured Query Language,' and it is a database query language. SQL is the standard query language used by ANSI for maintaining relational database management systems (RDBMS) and conducting various data manipulation operations on various types of data. It is a database language that is used to create and delete databases, as well as to fetch and edit table rows and a variety of other tasks.
DDL stands for Data Definition Language, and it is the part of SQL that defines the database's data structure when it is being built for the first time. It's mostly used for creating and reorganizing database items.
DML (Data Manipulation Language) is a programming language that is used to manipulate data in a database. In other words, it aids users in retrieving and manipulating data. It's used to do things like insert data into the database, update data using the update command, and delete data from the database with the delete command.
Data Control Language (DCL) is a programming language that is used to manage database data access. DCL commands are commonly used to generate user access objects and to manage the distribution of privileges across users. Grant and Revoke are the commands that are utilized in DCL.
Transaction Control Language (TCL) is a programming language that is used to manage the changes produced by DML operations. It also allows the assertions to be linked together to form logical transactions. Commit, Rollback, Savepoint, Begin, and Transaction are the commands used in TCL.
There are four types of database management systems:
Data is kept in a hierarchical format in a tree-like structure called a hierarchical database. The parent may have multiple children in this database, but each child should have only one parent.
The network database is displayed as a graph with many-to-many relationships. Children can have many children in this database.
A relational database is represented in the form of a table. The values in the columns and rows are interrelated. Because it is simple to use, it is the most extensively used database.
Object-Oriented Database: This database stores data values and processes as objects. There are various relationships between all of these objects.
What is the definition of a default constraint?
Constraints are used to set data processing rules and to limit the types of data that may be entered into a table. Let's look at the default constraint now.
The default constraint is used to specify a column's default value, which will be applied to all new records if no alternative value is specified. For example, if we give a default constraint to the E salary column in the below table and set the default value to 85000, then all entries in this column will have this value until another value is assigned during insertion.
In SQL, what do you mean by table and field?
A table is a collection of ordered data in the form of rows and columns. Tuples and attributes are used to refer to rows and columns.
A field is defined as the number of columns in a table. Fields in a record represent qualities and attributes.
What is a one-of-a-kind constraint?
Unique constraints ensure that each column's values are distinct. For example, if the e name column in the table below has a unique constraint, then each entry in this column should have a unique value.
What is the definition of a primary key?
All table records are uniquely identified by a primary key. It can't have any NULL values, and it has to be unique. A table can only have one primary key, which can be made up of one or more fields.
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