SQLite Interview Questions and Answers

This section covers a range of SQLite interview questions, focusing on its features, syntax, and common operations.

1. What is SQLite?

SQLite is a lightweight, embedded, serverless, and zero-configuration relational database management system. It's often used in applications where a full-fledged database server is not needed.

2. Who Designed SQLite?

D. Richard Hipp.

3. Key Features of SQLite.

  • Free and open-source
  • Serverless (no separate database server required)
  • Zero configuration
  • Cross-platform
  • Self-contained

4. Advantages of Using SQLite.

  • Lightweight and efficient.
  • Simple to use and learn.

5. Creating a Database in SQLite.

Use the sqlite3 command (e.g., sqlite3 mydatabase.db).

6. Creating a Table in SQLite.

Syntax

CREATE TABLE table_name (
  column1 datatype PRIMARY KEY,
  column2 datatype,
  column3 datatype,
  ...
);

7. Dropping a Table in SQLite.

Syntax

DROP TABLE table_name;

8. Creating an AUTOINCREMENT Field.

Declare a column as INTEGER PRIMARY KEY. SQLite automatically handles auto-incrementing values.

9. Data Types in SQLite.

SQLite uses dynamic typing. Data types include:

  • INTEGER
  • REAL
  • TEXT
  • BLOB (binary large object)
  • NULL

10. Inserting Data in SQLite.

Syntax

INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);

11. Retrieving Data from SQLite Tables.

Syntax

SELECT column1, column2, ... FROM table_name;

12. UPDATE Queries in SQLite.

Syntax

UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;

13. Deleting Records in SQLite.

Syntax

DELETE FROM table_name WHERE condition;

14. The WHERE Clause.

The WHERE clause specifies conditions for filtering rows in SELECT, UPDATE, and DELETE statements.

15. AND and OR Operators.

AND and OR combine multiple conditions in a WHERE clause.

16. The LIKE Operator.

LIKE performs pattern matching on strings using wildcards (% and _).

17. The LIMIT Clause.

LIMIT restricts the number of rows returned by a SELECT query.

18. The ORDER BY Clause.

ORDER BY sorts the results of a SELECT query in ascending (ASC) or descending (DESC) order.

19. The GROUP BY Clause.

GROUP BY groups rows with the same values in specified columns.

20. The DISTINCT Clause.

DISTINCT in a SELECT statement returns only unique rows, eliminating duplicates.

21. The UNION Operator.

UNION combines the result sets of two or more SELECT statements, removing duplicates.

22. UNION vs. UNION ALL.

UNION ALL combines result sets, including duplicates.

23. JOIN Operations in SQLite.

Joins combine data from multiple tables. SQLite supports INNER JOIN, LEFT OUTER JOIN, and CROSS JOIN.

24. INNER JOIN.

Returns only matching rows from both tables.

25. OUTER JOIN (Left Outer Join).

Returns all rows from the left table, and the matching rows from the right table; unmatched rows from the right table get NULLs.

26. CROSS JOIN.

Creates a Cartesian product (all possible combinations) of rows from both tables.

27. Date and Time Functions.

SQLite provides functions for working with dates and times (date(), datetime(), julianday(), strftime(), time(), `now()`).

28. DATE() Function

The DATE() function extracts the date (year, month, and day) from a datetime string or timestamp.

Syntax

SELECT DATE('2025-01-01 12:00:00');
Output

2025-01-01

29. TIME() Function

The TIME() function retrieves only the time portion (hours, minutes, and seconds) from a given datetime string or timestamp.

Syntax

SELECT TIME('2025-01-01 12:30:45');
Output

12:30:45

30. DATETIME() Function

The DATETIME() function returns both the date and the time in the 'YYYY-MM-DD HH:MM:SS' format.

Syntax

SELECT DATETIME('2025-01-01 12:30:45');
Output

2025-01-01 12:30:45

31. JULIANDAY() Function

The JULIANDAY() function returns the Julian day number, which is a continuous count of days since January 1, 4713 BC, in a decimal format.

Syntax

SELECT JULIANDAY('2025-01-01 12:00:00');
Output

2458876.5

32. STRFTIME() Function

The STRFTIME() function allows you to format a datetime string into a specified format using format specifiers.

Syntax

SELECT STRFTIME('%Y-%m-%d %H:%M:%S', '2025-01-01 12:30:45');
Output

2025-01-01 12:30:45

33. CURRENT_DATE Function

The CURRENT_DATE function returns the current date in the format 'YYYY-MM-DD'. It is useful for retrieving the system's current date without needing any arguments.

Syntax

SELECT CURRENT_DATE;
Output

2025-01-06 (or current date)

SQLite's date and time functions are versatile and can be used for a wide variety of date-related operations. From extracting specific components to converting formats or calculating intervals, these functions provide the flexibility you need for working with dates and times in your SQLite database.

34. SQLite Aggregate Functions.

Aggregate functions perform calculations on multiple rows and return a single value.

35. MIN() Aggregate Function.

Syntax

SELECT MIN(column_name) FROM table_name;

36. MAX() Aggregate Function.

Syntax

SELECT MAX(column_name) FROM table_name;

37. AVG() Aggregate Function.

Syntax

SELECT AVG(column_name) FROM table_name;

38. COUNT() Aggregate Function.

Syntax

SELECT COUNT(column_name) FROM table_name;

39. SUM() Aggregate Function.

Syntax

SELECT SUM(column_name) FROM table_name;

40. SQL vs. SQLite.

Feature SQL SQLite
Nature Language Database system
Stored Procedures Supported Not supported

41. SQLite Transactions.

A transaction in SQLite is a sequence of database operations treated as a single unit of work, following ACID properties (Atomicity, Consistency, Isolation, Durability).

42. Where SQLite is Preferred.

  • Embedded systems
  • Application file formats
  • Data analysis
  • Websites
  • File archives
  • Caches
  • Temporary databases

43. The .dump Command.

The .dump command creates a text file containing a backup of a SQLite database. This is a useful way to back up the contents of your database.