After reading our top 30 PostgreSQL interview questions with answers for beginners and intermediate level candidates, you know exactly what interviewers are looking for in an applicant. You can use this list to prepare yourself and nail your next postgreSQL query interview without any stress.
Top 30 PostgreSQL Interview Questions and Answers for 2022
1. What does a PostgreSQL partitioned table look like?
The partitioned table is a logical structure. It is used to split a large table into smaller pieces, which are called partitions.
2. How can you avoid locking a database unnecessarily?
We can use MVCC (Multi-version concurrency control) to avoid unnecessary locking of a database.
3. What purpose does pgAdmin serve in PostgreSQL?
The pgAdmin in PostgreSQL is a data administration tool. It serves the purpose of retrieving, developing, testing, and maintaining databases.
4. What is the PostgreSQL feature called that splits a large table into smaller pieces?
It is called table partitioning.
5. What do you know about PL/Python?
PL/Python is a procedural language to which PostgreSQL provides support.
6. What methods does PostgreSQL provide to create a new database?
PostgreSQL provides the following methods to create a new database:
- Using CREATE DATABASE, an SQL command
2. Using created a command-line executable
7. What would be the most important pieces of information you would want to include in a schema?
A schema contains tables along with data types, views, indexes, operators, sequences, and functions.
8. What are some of the different operators in PostgreSQL?
The PostgreSQL operators include - Arithmetic operators, Comparison operators, Logical operators, and Bitwise operators.
9. How can you delete a PostgreSQL database?
We can delete the database by using any one of the below options:
- Using DROP DATABASE, an SQL command
- Using dropdb a command-line executable
10. What do you think indexes are used for?
Indexes are used by the search engine to speed up data retrieval.
11. What do you think is a Cluster index's purpose?
Cluster index sorts table data rows based on their key values.
12. What do you think are database call back functions? How do they help your application?
The database call back functions are called PostgreSQL Triggers. When a specified database event occurs, the PostgreSQL Triggers are performed or invoked automatically.
13. What are the benefits of specifying data types in columns while creating a table?
Some of these benefits include consistency, compactness, validation, and performance.
14. What do you need to do to update statistics in PostgreSQL?
To update statistics in PostgreSQL, we need to use a special function called a vacuum.
15. What do you think is the disadvantage of the DROP TABLE command?
Though the DROP TABLE command has the ability to delete complete data from an existing table, the disadvantage with it is - it removes complete table structure from the database. Due to this, we need to re-create a table to store data.
16. How can you completely delete a table?
We can delete complete data from an existing table using the PostgreSQL TRUNCATE TABLE command.
17. What are the different properties of a transaction in PostgreSQL? Which acronym is used to refer to them?
The properties of a transaction in PostgreSQL include Atomicity, Consistency, Isolation, and Durability. These are referred to by the acronym, namely ACID.
18. What purpose does the CTIDs field serve?
The CTIDs field identifies the specific physical rows in a table according to their block and offsets positions in that table.
19. Which are the commands used to control transactions in PostgreSQL?
The commands used to control transactions in PostgreSQL are BEGIN TRANSACTION, COMMIT, and ROLLBACK.
20. What are the main differences between SQL and PostgreSQL?
PostgreSQL is an advanced version of SQL. Some of the differences between these two include the following:
- Unlike SQL, views in PostgreSQL are not updatable.
- Another difference is that SQL provides computed columns; the same cannot be expected from PostgreSQL.
- Unlike SQL, in PostgreSQL, you don’t need to create a DLL to see what the code is doing.
- PostgreSQL supports dynamic actions whereas SQL doesn’t support them.
21. How is security ensured in PostgreSQL?
PostgreSQL uses SSL connections to encrypt client or server communications so that security will be ensured.
22. What is the function of the Atomicity property in PostgreSQL?
Atomicity property ensures the successful completion of all the operations in a work unit.
23. What do you think are some of the advantages of using PostgreSQL?
Some of the advantages of PostgreSQL are open-source DBMS, community support, ACID compliance, diverse indexing techniques, full-text search, a variety of replication methods, and diversified extension functions, etc.
24. How does Write-Ahead Logging help you?
The Write-Ahead Logging enhances database reliability by logging changes before any changes or updates are made to the database
25. What are some of the important PostgreSQL administration tools?
Some of the important data administration tools supported by PostgreSQL are Psql, Pgadmin, and Phppgadmin.
26. How do you think you can store binary data in PostgreSQL?
We can store the binary data in PostgreSQL either by using bytes or by using the large object feature.
27. What do you think of the term "non-clustered index"?
In a non-clustered index, the index row order doesn’t match the order in actual data.
28. What purpose do you think table space serves in PostgreSQL?
It is a location in the disk. In this, PostgreSQL stores the data files, which contain indices and tables, etc.
29. Do you think there are any disadvantages with PostgreSQL?
Yes. There are a few disadvantages. Some of these include the following:
- It is slower than MySQL on the performance front.
- It doesn’t have the support of a good number of open source applications when compared to MySQL.
- Since it focuses more on compatibility, changes made to improve the speed need more work.
30. What does a token in a SQL statement represent?
In a SQL Statement, a token represents an identifier, keyword, quoted identifier, special character symbol, or a constant.
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