Top 05 Advance SQL Interview Questions (2024)

1. Explain the difference between a clustered and a non-clustered index.

[{"selector":"#anim-7a1d273f-6907-4e27-aca1-a08e4234f1f8 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(0%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-f46e7f92-1976-4740-88e1-6dc54748f63b","keyframes":{"opacity":[0,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-3cbbdf36-1908-4989-8bc9-bb097024efda","keyframes":{"transform":["translate3d(0px, -1092.59224%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-f9848628-3de5-48c2-8eb2-af35dbca2476","keyframes":{"opacity":[0,1]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-08c15803-f5e8-491f-a042-6242d805bd6f","keyframes":{"transform":["translate3d(0px, 256.53020%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] www.devstringx.com This question assesses the candidate's understanding of database indexing strategies, which are crucial for performance tuning.

2. How can you optimize a slow-running SQL query?

[{"selector":"#anim-744b2e6a-56e2-414c-9f80-be1252dae2b1 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(0%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-629a49e3-98c2-4421-a704-aec72075bb77","keyframes":{"opacity":[0,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-9779cb7b-4710-4c77-850d-ed7d877d62d5","keyframes":{"transform":["translate3d(0px, -1092.59224%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-682f6ee2-83ec-426c-87c8-601a3129ce4a","keyframes":{"opacity":[0,1]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-a55c11b0-baee-403a-8280-bfc7679a983d","keyframes":{"transform":["translate3d(0px, 256.53020%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] www.devstringx.com Candidates should be able to discuss strategies like indexing, query refactoring, using joins instead of subqueries.

3. What is a database transaction and how does ACID play a role in it?

[{"selector":"#anim-6269836a-019a-40c7-a041-519cd2d29686 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(0%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-5702994c-8e04-4f90-8216-b368398d7432","keyframes":{"opacity":[0,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-85d43f6d-4959-4eb6-aad4-9e86a185bdf0","keyframes":{"transform":["translate3d(0px, -1092.59224%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-b6dd4631-b6b6-4cf7-80d1-8879a6444238","keyframes":{"opacity":[0,1]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-a0b757d1-e0aa-4935-8be4-36d10bdb2bac","keyframes":{"transform":["translate3d(0px, 189.89891%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] www.devstringx.com This question probes the candidate’s understanding of the transactional integrity of a database system which is crucial for ensuring data correctness and handling concurrency.

4. How would you implement pagination in SQL queries?

[{"selector":"#anim-2dfb13b6-f2eb-4f35-94bf-4499ff4846de [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(0%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-0a350e02-2ecd-4b65-bb74-012ca8c82873","keyframes":{"opacity":[0,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-0192c876-a28f-4542-a474-354dce29641f","keyframes":{"transform":["translate3d(0px, -1092.59224%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-e015964c-67cc-410e-965b-c68a20311de1","keyframes":{"opacity":[0,1]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-6e130e02-6382-44a0-bef5-cfbec885ba0b","keyframes":{"transform":["translate3d(0px, 395.19480%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] www.devstringx.com Pagination is essential for handling large datasets in applications.

5. Explain the difference between HAVING and WHERE clause.

[{"selector":"#anim-bdda6900-949b-4db7-8062-080e2acd4421 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(0%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-007f1e5b-bd05-4ac6-bcd8-a309068bb1e3","keyframes":{"opacity":[0,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-e3dfe35b-096e-4f28-b08b-6bf23b1d3a5b","keyframes":{"transform":["translate3d(0px, -1092.59224%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-d14a7393-1297-4861-a7b9-14b0b5cb41df","keyframes":{"opacity":[0,1]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-bdc8d40d-9573-41fc-af63-0aef899c3136","keyframes":{"transform":["translate3d(0px, 256.53020%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":1000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] www.devstringx.com This tests knowledge of SQL syntax, specifically the difference in filtering aggregated vs. non-aggregated data.

Check out our latest story on Top 05 Benefits of NOSQL (2024)

[{"selector":"#anim-df6e38cd-80ad-4db0-9c58-753c1a6ca9c2 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate(0%, 0%) scale(1.5)","translate(0%, 0%) scale(1)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] [{"selector":"#anim-0a712c1b-c10f-4833-9f13-10789560d430","keyframes":{"opacity":[0,1]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-7316b716-719b-4c91-844b-82d49f0092f5","keyframes":{"transform":["translate3d(0px, -843.41878%, 0)","translate3d(0px, 0px, 0)"]},"delay":0,"duration":2000,"easing":"cubic-bezier(0.2, 0.6, 0.0, 1)","fill":"both"}] [{"selector":"#anim-1fcd773c-b17c-4be1-92a6-59c504f367d4","keyframes":{"opacity":[0,1]},"delay":0,"duration":600,"easing":"cubic-bezier(0.4, 0.4, 0.0, 1)","fill":"both"}] [{"selector":"#anim-9417c8cb-af08-47a6-803d-edf4397ac10d","keyframes":{"transform":["scale(1)","scale(1.5)","scale(0.95)","scale(1)"],"offset":[0,0.33,0.66,1]},"delay":0,"duration":1450,"easing":"ease-in-out","fill":"both","iterations":5}] www.devstringx.com