| Section A – SQL Basics |
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| 1 |
What are the different types of SQL commands (DDL, DML, DCL, TCL)? |
Infosys, TCS |
Easy |
Theory |
Most frequent |
| 2 |
Difference between SQL and NoSQL databases. |
Amazon, Google |
Medium |
Theory |
Normal |
| 3 |
Explain difference between DELETE, TRUNCATE, and DROP. |
Microsoft, Accenture |
Easy |
Theory |
Most frequent |
| 4 |
What are primary keys and foreign keys? |
TCS, Cognizant |
Easy |
Theory |
Most frequent |
| 5 |
Difference between CHAR, VARCHAR, and TEXT. |
Amazon, Flipkart |
Easy |
Theory |
Normal |
| 6 |
What are constraints in SQL? Explain with examples. |
Infosys, Wipro |
Easy |
Theory |
Most frequent |
| 7 |
What is the difference between UNION and UNION ALL? |
Google, Meta |
Medium |
Theory + Practical |
Most frequent |
| 8 |
Explain NULL in SQL and how it is handled in comparisons. |
Amazon, Microsoft |
Medium |
Theory |
Most frequent |
| 9 |
Difference between IN and EXISTS. |
Flipkart, TCS |
Medium |
Both |
Normal |
| 10 |
What is a subquery? Give types. |
Amazon, Wipro |
Medium |
Theory + Practical |
Most frequent |
| Section B – Joins |
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| 11 |
Difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN. |
Amazon, Microsoft |
Medium |
Both |
Most frequent |
| 12 |
What is a SELF JOIN? Provide use case. |
Infosys, TCS |
Medium |
Practical |
Normal |
| 13 |
Difference between CROSS JOIN and FULL OUTER JOIN. |
Google, Accenture |
Medium |
Theory |
Normal |
| 14 |
How to find unmatched records using joins? |
Amazon, Flipkart |
Medium |
Practical |
Most frequent |
| 15 |
Explain natural join and its risks. |
Infosys, Cognizant |
Medium |
Theory |
Medium |
| Section C – Aggregations & Grouping |
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| 16 |
Difference between COUNT(*) and COUNT(column). |
Amazon, Microsoft |
Easy |
Theory |
Most frequent |
| 17 |
What is the HAVING clause? How is it different from WHERE? |
Google, Infosys |
Medium |
Both |
Most frequent |
| 18 |
Explain GROUP BY with example. |
Amazon, Flipkart |
Easy |
Practical |
Most frequent |
| 19 |
How do you calculate median in SQL? |
Microsoft, Meta |
Hard |
Practical |
Normal |
| 20 |
Difference between RANK, DENSE_RANK, and ROW_NUMBER. |
Amazon, Google |
Medium |
Practical |
Most frequent |
| Section D – Window Functions |
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| 21 |
What are window functions in SQL? |
Google, Microsoft |
Medium |
Theory |
Most frequent |
| 22 |
Difference between PARTITION BY and GROUP BY. |
Amazon, Meta |
Medium |
Both |
Most frequent |
| 23 |
How to calculate running totals using SQL? |
Flipkart, Infosys |
Medium |
Practical |
Normal |
| 24 |
What is LAG and LEAD in SQL? |
Amazon, Microsoft |
Medium |
Practical |
Most frequent |
| 25 |
How to calculate moving averages in SQL? |
Google, TCS |
Medium |
Practical |
Normal |
| Section E – Indexing & Optimization |
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| 26 |
What are indexes in SQL? Why are they used? |
Amazon, Google |
Medium |
Theory |
Most frequent |
| 27 |
Difference between clustered and non-clustered index. |
Microsoft, Infosys |
Medium |
Theory |
Most frequent |
| 28 |
What is a composite index? |
Amazon, Flipkart |
Medium |
Theory |
Normal |
| 29 |
What is index selectivity? |
Google, Meta |
Hard |
Theory |
Normal |
| 30 |
How would you identify slow queries? |
Amazon, Microsoft |
Hard |
Both |
Normal |
| Section F – Data Types & Functions |
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| 31 |
Difference between DATE, DATETIME, and TIMESTAMP. |
Infosys, TCS |
Medium |
Theory |
Most frequent |
| 32 |
How to extract year, month, and day from a DATE column? |
Amazon, Google |
Easy |
Practical |
Most frequent |
| 33 |
Difference between CAST and CONVERT. |
Microsoft, Accenture |
Medium |
Both |
Normal |
| 34 |
How to round, truncate, and format numbers in SQL? |
Infosys, Wipro |
Easy |
Practical |
Most frequent |
| 35 |
Difference between CHARINDEX and PATINDEX. |
Amazon, TCS |
Medium |
Practical |
Medium |
| 36 |
What are string functions in SQL? |
Flipkart, Microsoft |
Easy |
Practical |
Most frequent |
| 37 |
How do you concatenate strings in SQL? |
Infosys, Cognizant |
Easy |
Practical |
Most frequent |
| 38 |
How to split strings in SQL? |
Amazon, TCS |
Medium |
Practical |
Normal |
| 39 |
How to find length of string and trim spaces? |
Microsoft, Infosys |
Easy |
Practical |
Most frequent |
| 40 |
How to replace substrings in SQL? |
Google, Amazon |
Easy |
Practical |
Most frequent |
| Section G – Normalization & Schema Design |
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| 41 |
What is database normalization? Why is it needed? |
Infosys, TCS |
Medium |
Theory |
Most frequent |
| 42 |
Explain 1NF, 2NF, 3NF, and BCNF. |
Amazon, Google |
Medium |
Theory |
Most frequent |
| 43 |
Difference between denormalization and normalization. |
Microsoft, Flipkart |
Medium |
Theory |
Normal |
| 44 |
What is a surrogate key vs natural key? |
Infosys, Cognizant |
Medium |
Theory |
Normal |
| 45 |
What is data redundancy and how to handle it? |
Amazon, TCS |
Medium |
Theory |
Normal |
| Section H – Transactions |
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| 46 |
What is ACID property in databases? |
Amazon, Infosys |
Easy |
Theory |
Most frequent |
| 47 |
Explain transaction isolation levels. |
Google, Microsoft |
Hard |
Theory |
Most frequent |
| 48 |
Difference between COMMIT and ROLLBACK. |
Infosys, TCS |
Easy |
Practical |
Most frequent |
| 49 |
What is a savepoint? |
Microsoft, Wipro |
Medium |
Practical |
Normal |
| 50 |
Difference between pessimistic and optimistic locking. |
Amazon, Google |
Hard |
Theory |
Medium |
| Section I – Advanced Queries |
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| 51 |
What is a CTE (Common Table Expression)? |
Amazon, Microsoft |
Medium |
Theory + Practical |
Most frequent |
| 52 |
Difference between CTE and Subquery. |
Google, Infosys |
Medium |
Theory |
Normal |
| 53 |
What are recursive CTEs? |
Amazon, TCS |
Hard |
Practical |
Medium |
| 54 |
Difference between temporary table and table variable. |
Microsoft, Cognizant |
Medium |
Both |
Normal |
| 55 |
What is a materialized view? |
Amazon, Google |
Hard |
Theory |
Medium |
| 56 |
Difference between View and Table. |
Infosys, TCS |
Medium |
Theory |
Most frequent |
| 57 |
What are stored procedures? |
Microsoft, Wipro |
Medium |
Theory + Practical |
Most frequent |
| 58 |
Difference between functions and stored procedures. |
Amazon, Infosys |
Medium |
Both |
Most frequent |
| 59 |
What are triggers in SQL? |
Google, Flipkart |
Medium |
Both |
Normal |
| 60 |
Difference between AFTER and INSTEAD OF triggers. |
Microsoft, Amazon |
Hard |
Theory |
Medium |
| Section J – Performance Tuning |
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| 61 |
How do you use EXPLAIN or EXPLAIN PLAN? |
Amazon, Google |
Medium |
Practical |
Normal |
| 62 |
How to optimize a slow query? |
Microsoft, Infosys |
Hard |
Both |
Most frequent |
| 63 |
What are query execution plans? |
Amazon, Wipro |
Medium |
Theory |
Normal |
| 64 |
Difference between OLAP and OLTP. |
Google, Accenture |
Medium |
Theory |
Most frequent |
| 65 |
What are database partitions? |
Microsoft, Infosys |
Hard |
Theory |
Normal |
| 66 |
Difference between horizontal and vertical partitioning. |
Amazon, Flipkart |
Medium |
Theory |
Medium |
| 67 |
What are sharding and replication? |
Google, Meta |
Hard |
Theory |
Medium |
| 68 |
What is indexing strategy for large tables? |
Amazon, Microsoft |
Hard |
Theory |
Medium |
| 69 |
How do you detect deadlocks? |
Infosys, TCS |
Hard |
Both |
Normal |
| 70 |
How do you resolve locking issues? |
Microsoft, Amazon |
Hard |
Both |
Normal |
| Section K – Security & Access |
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| 71 |
What is SQL injection? How to prevent it? |
Google, Microsoft |
Medium |
Theory |
Most frequent |
| 72 |
Difference between user and role in SQL. |
Infosys, TCS |
Medium |
Theory |
Normal |
| 73 |
How to grant and revoke permissions in SQL? |
Amazon, Wipro |
Easy |
Practical |
Normal |
| 74 |
What are database roles and privileges? |
Google, Microsoft |
Medium |
Theory |
Normal |
| 75 |
How to audit changes in a database? |
Amazon, Infosys |
Hard |
Practical |
Medium |
| Section L – Miscellaneous |
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| 76 |
Difference between OLAP cube and relational DB. |
Microsoft, Infosys |
Hard |
Theory |
Medium |
| 77 |
How do you pivot rows into columns in SQL? |
Amazon, Flipkart |
Medium |
Practical |
Most frequent |
| 78 |
How do you unpivot columns into rows? |
Google, TCS |
Medium |
Practical |
Normal |
| 79 |
What is the difference between RDBMS and DBMS? |
Infosys, Cognizant |
Easy |
Theory |
Most frequent |
| 80 |
Difference between SQL and PL/SQL. |
Oracle, TCS |
Medium |
Theory |
Normal |
| 81 |
What are SQL window frames? |
Amazon, Google |
Hard |
Theory |
Normal |
| 82 |
What are recursive queries used for? |
Microsoft, Flipkart |
Hard |
Practical |
Medium |
| 83 |
How do you create hierarchical queries? |
Oracle, Infosys |
Hard |
Practical |
Medium |
| 84 |
What is query caching? |
Google, Amazon |
Medium |
Theory |
Normal |
| 85 |
What are JSON functions in SQL? |
Microsoft, Amazon |
Medium |
Practical |
Normal |
| 86 |
How to store unstructured data in SQL databases? |
Google, Infosys |
Medium |
Theory |
Medium |
| 87 |
Difference between normalized and star schema. |
Amazon, TCS |
Medium |
Theory |
Most frequent |