Comprehensive, community-driven list of essential SQL interview questions. Whether you're a candidate or interviewer, these interview questions will help prepare you for your next SQL interview ahead of time.
OLTP (Online Transaction Processing) – Optimized for fast, transactional queries (e.g., banking, e-commerce). OLAP (Online Analytical Processing) – Designed for complex queries, reporting, and business intelligence. FeatureOLTPOLAP Query TypeRead/WriteRead-heavy Data ModelNormalizedDenormalized SpeedM...
High percentage of Signal Wait:Signal wait is the time a worker spends waiting for CPU time after it has finished waiting on something else (such as a lock, a latch or some other wait). Time spent waiting on the CPU is indicative of a CPU bottleneck. Signal wait can be found by execu...
7. Write a query to delete duplicate records from a table. Note: Write queries that suits the below situation. A table is having a unique key and having duplicates records, table is not having a unique and having duplicate records. 8. What is XACT_ABORT ON? 9. How to filter nested st...
Joins are used in queries to explain how different tables are related. Joins also let you select data from a table depending upon data from another table. Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs.OUTER JOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS and FULL...
Functions, on the other hand, return a value after performing operations. They are suitable for calculations or data retrieval that need to return a result. The function below simplifies fetching an employee's salary, making it reusable in SQL queries or other procedures. ...
A view is a virtual table based on one or more tables. Why Use views ? To restrict data access • To make complex queries easy • To provide data independence • To present different views of the same data Q. What are the advantages of Views ?
A table stores and retrieves data from persistent storage whenever the user wants. On the other side, the view is only a virtual table based on the result of some SQL queries, meaning that this will disappear after the session ends. ...
A view is a virtual table based on aSELECTquery that can join and simplify complex queries, encapsulate logic, and provide a layer of abstraction. Views enhance security by restricting access to underlying tables, simplify data access, and present a consistent, unchanging schema even if the under...
You get these on a workday you choose, and you’ll have ~12 hours to solve it and send the solution back (SQL queries and a short presentation). I like this assessment type, as it creates a less stressful environment for the applicant. Automated SQL screening. With the rise of remote...