Top 80 SQL job interview questions

SQL stands for structured query language, and it is one of the most in-demand talents for any job today that requires working with data and databases. Professionals that have mastered SQL are in high demand in the business. Recruiters are constantly on the hunt for such candidates.

There are a lot of resources online for SQL if you’d like to familiarize yourself with it however if you’re serious about a career in IT and data you may want to look into attending a SQL training course to make sure you have a good foundation to build on. How to Install Microsoft SQL Server Here is a step-by-step process on how to install SQL.

You must have a thorough comprehension of all SQL concepts if you want to work as a data analyst, data scientist, data engineer, data administrator, or web developer. If you want to ace a SQL job interview, you should familiarize yourself with the SQL questions that are frequently used to assess your technical abilities. Here is a list of the ten most difficult SQL job interview questions.

1. How to enhance the speed of a stored procedure?
2. How to remove duplicate rows from the table?
3. What is ACID property in a database?
4. How do you check whether the date passed to Query is the date of given format or not? Write an SQL Query to show.
5. If you are a SQL Developer, how can you delete duplicate records in a table with no primary key?
6. Write SQL Query to fetch employee names having a salary greater than or equal to 5000 and less than or equal 10000?
7. Can you tell the sixth normal form in SQL server?
8. Can you tell in which files does SQL server actually store data?
9. How to find the maximum salary in each department of an organization? Write an SQL Query to show.
10. Tell the major difference between the RANK() and DENSE_RANK() functions? Give an example.
11. What is Database?
12. What is DBMS?
13. What is RDBMS? How is it different from DBMS?
14. What is SQL?
15. What is the difference between SQL and MySQL?
16. What are Tables and Fields?
17. What are Constraints in SQL?
18. What is a Primary Key?
19. What is a UNIQUE constraint?
20. What is a Foreign Key?
21. What is a Join? List its different types.
22. What is a Self-Join?
23. What is a Cross-Join?
24. What is an Index? Explain its different types.
25. What is the difference between Clustered and Non-clustered index?
26. What is Data Integrity?
27. What is a Query?
28. What is a Subquery? What are its types?
29. What is the SELECT statement?
30. What are some common clauses used with SELECT query in SQL?
31. What are UNION, MINUS and INTERSECT commands?
32. What is Cursor? How to use a Cursor?
33. What are Entities and Relationships?
34. List the different types of relationships in SQL.
35. What is an Alias in SQL?
36. What is a View?
37. What is Normalization?
38. What is Denormalization?
39. What are the various forms of Normalization?
40. What are the TRUNCATE, DELETE and DROP statements?
41. What is the difference between DROP and TRUNCATE statements?
42. What is the difference between DELETE and TRUNCATE statements?
43. What are Aggregate and Scalar functions?
44. What is User-defined function? What are its various types?
45. What is OLTP?
46. What are the differences between OLTP and OLAP?
47. What is Collation? What are the different types of Collation Sensitivity?
48. What is a Stored Procedure?
49. What is a Recursive Stored Procedure?
50. How to create empty tables with the same structure as another table?
51. What is Pattern Matching in SQL?
52. PostgreSQL Interview Questions
53. What is PostgreSQL?
54. How do you define Indexes in PostgreSQL?
55. How will you change the datatype of a column?
56. What is the command used for creating a database in PostgreSQL?
57. How can we start, restart and stop the PostgreSQL server?
58. What are partitioned tables called in PostgreSQL?
59. Define tokens in PostgreSQL?
60. What is the importance of the TRUNCATE statement?
61. What is the capacity of a table in PostgreSQL?
62. Define sequence?
63. What are string constants in PostgreSQL?
64. How can you get a list of all databases in PostgreSQL?
65. How can you delete a database in PostgreSQL?
66. What are ACID properties? Is PostgreSQL compliant with ACID?
67. Can you explain the architecture of PostgreSQL?
68. What do you understand by multi-version concurrency control?
69. What do you understand by command enable-debug?
70. How do you check the rows affected as part of previous transactions?
71. What can you tell about WAL (Write Ahead Logging)?
72. What is the main disadvantage of deleting data from an existing table using the DROP TABLE command?
73. How do you perform case-insensitive searches using regular expressions in PostgreSQL?
74. How will you take backup of the database in PostgreSQL?
75. Does PostgreSQL support full text search?
76. What are parallel queries in PostgreSQL?
77. Differentiate between commit and checkpoint.

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