SQL Interview Questions and Answers

1. How will you differentiate between Varchar & Varchar2?

2. What are the components of logical database structure in Oracle database?

3. Describe an Oracle table

4. Explain the relationship among database, tablespace and data file?

5. What are the various Oracle database objects?

6. Explain about the ANALYZE command in Oracle?

7. What types of joins are used in writing subqueries?

8. RAW datatype in Oracle

9. What is the use of Aggregate functions in Oracle?

10. Explain Temporal data types in Oracle

11. What is a View?

12. How to store pictures on to the database?

13. Where do you use DECODE and CASE Statements?

14. What do you mean by Merge in Oracle and how can you merge two tables?

15. What is the data type of DUAL table?

16. Explain about integrity constraint?

17. What is SQL and also describe types of SQL statements?

18. Briefly explain what is Literal? Give an example where it can be used?

19. How to display row numbers with the records?

20. What is the difference between SQL and iSQL*Plus?

21. What are SQL functions? Describe in brief different types of SQL functions?

22. Describe different types of General Function used in SQL?

23. What is a Sub Query? Describe its Types?

24. What is the use of Double Ampersand (&&) in SQL Queries? Give an example

25. Describe VArray

26. What are the attributes of the Cursor?

27. Name the various constraints used in Oracle

28. What is the fastest query method to fetch data from the table?

29. Difference between Cartesian Join and Cross Join?

30. How does the ON-DELETE-CASCADE statement work?

31. What is PL SQL?

32. Enlist the characteristics of PL/SQL?

33. What are the data types available in PL/SQL?

34. What are the uses of a database trigger

35. Show how functions and procedures are called in a PL SQL block

36. What are the two virtual tables available at the time of database trigger execution?

37. What are the differences between Primary Key and Unique Key?

38. Explain the purpose of %TYPE and %ROWTYPE data types with the example?

39. Explain the difference between Triggers and Constraints?

40. Exception handling in PL/SQL

41. What is the difference between COUNT (*), COUNT (expression), COUNT (distinct expression)?

42. Difference between the “VERIFY” and “FEEDBACK” command?

43. List out the difference between Commit, Rollback, and Savepoint?

44. What is the difference between SUBSTR and INSTR?

45. Point out the difference between USER TABLES and DATA DICTIONARY?

46. Major difference between Truncate and Delete?

47. Point the difference between TRANSLATE and REPLACE?

48. What is the difference between $ORACLE_BASE and $ORACLE_HOME?

49. What do you understand by Redo Log file mirroring?

50. What is the difference between a hot backup and a cold backup in Oracle? Explain about their benefits as well

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