Top 5 SQL Interview Questions for Freshers Asked in Interview

By Arzoo Yadav Published: 13 March, 2025 Image: Pixabay [{ "selector": ".aninn-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-57.5px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

Mastering SQL is essential for cracking technical interviews and securing high-paying jobs in the IT industry. Image: Pixabay [{ "selector": ".xzmcl-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".epcgq-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-47px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

SQL is a programming language used to manage and manipulate databases. It is used for querying, updating, and managing data in relational databases. Image: Pixabay [{ "selector": ".iuszz-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".jolml-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-68px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

Let's dive into the 5 most common SQL interview questions. Image: Pixabay [{ "selector": ".nqojf-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".cekxe-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-36.5px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

Different Types of SQL Statements

DML: Retrieves, inserts, updates, and deletes data in a database. DDL: Creates and modifies database objects like tables, views, and indexes. TCL: Manages transactions within a database. Image: Pixabay [{ "selector": ".plxrg-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".erwgf-a", "duration": "500ms", "fill": "forwards", "delay": "500ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".ujukb-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-125.5px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

Difference Between Primary Key and Foreign Key

A primary key is a unique identifier for each record in a table. It ensures that each record can be uniquely identified. Image: Pixabay [{ "selector": ".zqdgi-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".ngmpg-a", "duration": "500ms", "fill": "forwards", "delay": "500ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".bfbnt-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-92.5px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

What is Normalisation?

Normalization is the process of organizing a database to reduce redundancy and improve data integrity. Image: Pixabay [{ "selector": ".ixgij-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".nfizt-a", "duration": "500ms", "fill": "forwards", "delay": "500ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".jsfpc-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-75px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

Difference Between WHERE and HAVING

WHERE: Filters records before aggregation. HAVING: Filters records after aggregation (used with GROUP BY) Image: Pixabay [{ "selector": ".glbwr-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".owazf-a", "duration": "500ms", "fill": "forwards", "delay": "500ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".jiuwt-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-91px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

What is a subquery?

A subquery is a query nested within another query. It can be used in SELECT, INSERT, UPDATE, or DELETE statements to retrieve a value or set of values for use in the main query. Image: Pixabay [{ "selector": ".ibdfr-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".cdnzo-a", "duration": "500ms", "fill": "forwards", "delay": "500ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".urpni-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-86.5px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }]

Top Recruiters

TCS Infosys Wipro Accenture Amazon Image: Pixabay [{ "selector": ".edeub-a", "duration": "1000ms", "fill": "forwards", "delay": "1000ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".kmrnj-a", "duration": "500ms", "fill": "forwards", "delay": "500ms", "keyframes": [ {"offset": 0, "transform": "translateX(calc(360px - 30px)) scale(0.15)", "opacity": "1", "visibility" :"visible"}, {"offset": 1, "transform": "translateX(0px) scale(1)", "opacity": "1", "visibility" :"visible"} ] }, { "selector": ".edrln-a", "duration": "500ms", "fill": "forwards", "delay": "0ms", "keyframes": [ {"offset": 0, "transform": "translateX(-85.5px)", "opacity": "1", "visibility" :"visible" }, {"offset": 1, "transform": "translateX(0)", "opacity": "1", "visibility" :"visible"} ] }] Know More