Most Frequently Asked PostgreSQL Interview Questions
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Introduction to PostgreSQL
PostgreSQL is one of the most often used languages for Object-Relational Database Management Systems. It is put to use mostly for huge web applications. It is an object-oriented, relational, open-source database system. It is incredibly potent and allows users to extend any system without difficulty. It extends the SQL language and employs multiple capabilities to safely scale and store complex data workloads.
Features of PostgreSQL
- Language support: PostgreSQL supports four standard procedural languages, including PL/pgSQL, PL/Tcl, PL/Perl, and PL/Python.
- Indexes: PostgreSQL indexes support B+ tree, hash, generalized search trees, and generalized inverted indexes. Individuals can also design their own personalized indexes.
- Views: Views that generate virtual tables are supported by PostgreSQL.
- Rules: PostgreSQL supports rules, which allow the rewriting of a query’s hierarchical structure.
- Inheritance: In PostgreSQL, a table may be configured to inherit attributes from a “parent” table via inheritance.
- User-defined functions: It facilitates the construction of practically all new database objects, including Casts, conversions, dataTypes, domains, functions, aggregate functions, and indexes, including custom indexes for custom kinds operator.
Interview Questions for PostgreSQL
1. What are the core advantages of PostgreSQL?
The following are some of PostgreSQL’s features:
- Relational object database.
- SQL support and extensibility
- API and database validation flexibility.
- MVCC and procedural languages,
- WAL and Client-Server.
2. List the various data types supported by PostgreSQL.
The following are some of the new data types added to PostgreSQL:
- Numeric types
- Character types
- Temporal types
- Geometric primitives
- Arbitrary precision numeric
- Arrays, etc.
3. What are PostgreSQL’s tokens?
In PostgreSQL, tokens serve as the building elements of source code. They are comprised of a variety of special character symbols. Tokens are keywords mainly made up of predefined SQL commands and meanings. Commands comprise a sequence of tokens separated by a semicolon (‘;’). These may comprise of a constant, a quoted identifier, additional identifiers, a keyword, or a constant. Typically, Whitespace separates tokens.
4. What are the PostgreSQL Indices?
Indexes are a special PostgreSQL tool used to improve data retrieval from databases. A database index is similar to a book index. An index provides access to all the values in the indexed columns.PostgreSQL indexes let the database server locate and retrieve specific rows contained within a particular framework. B-tree, hash, GiST, SP-GiST, GIN, and BRIN are other examples. In PostgreSQL, users are indeed free to create their own indices. However, indices increase the complexity of data processing operations and are rarely employed.
5. How do I set up a PostgreSQL database?
There are two ways to generate databases. The CREATE DATABASE SQL command comes first.
Using the following syntax, we may build the database:-CREATE DATABASE ;
The second approach makes use of the createdb command.
We could establish the database with the following syntax:- createdb [option…] [description].
Depending on the use scenario, the createDB command may take many arguments.
6. How you can create a table in PostgreSQL?
CREATE TABLE [IF NOT EXISTS] table_name ( column1 datatype(length) column_contraint, column2 datatype(length) column_contraint, . . . columnn datatype(length) column_contraint, table_constraints );
7. Contrast ‘PostgreSQL’ to ‘MongoDB’
8. What is PostgreSQL’s Multi-Version concurrency control?
9. What exactly is pgAdmin?
10. How is the database deleted in PostgreSQL?
Using the syntax, databases may be removed in PostgreSQL.DROP DATABASE [IF EXISTS] ;
Please note that only inactive databases can be discarded.
11. What does a schema consist of?
12. What are the most significant differences between SQL and PostgreSQL?
PostgreSQL is a sophisticated SQL variant. PostgreSQL views cannot be updated.PostgreSQL does not support calculated columns. However, it does provide functional indexes. In PostgreSQL, replication takes the form of reports. PostgreSQL provides actions that are dynamic.
The PostgreSQL server provides several levels of encryption and flexibility to improve data security from disclosure in an insecure network scenario. Meanwhile, the SQL server is designed to provide a safe database platform. To that end, it includes several capabilities that can encrypt data, decrease authorization, and protect data from unethical acts.
13. Explain Write-Ahead Logging in detail.
Write-ahead logging (WAL) is vital to Postgres’ durability and data consistency. All modifications are initially captured to this append-only log, then to the data files on disk. Using write-ahead logging, you can protect your data against corruption. As a result of this method, a complete record of all operations and alterations is maintained. It’s well-known that backing up database changes before implementing or updating them improves the stability of certain databases. A backup log is kept here in case the database fails. When Postgres enforces write operations, it creates WAL (e.g., INSERT, UPDATE, etc.). In situations when WAL creation exceeds the capability of WAL archival off-disk or where a high database load reduces archiver performance, WAL capacity is limited.
14. What is the definition of a non-clustered index?
A non-clustered index in PostgreSQL is a simple index used to quickly retrieve data with no assurance of uniqueness. It includes references to other places where data is kept. This is known as a secondary index too. You can have several indices of this category as you want on a given table. Non-clustered indexes are analogous to a document’s “Table of Contents.” We check the page number first, then the page numbers after that to view the entire content. It keeps a pointer to corresponding heap data to get the whole data based on an index. It’s exactly similar to knowing the page number and then going to that page to retrieve the actual content of the page.
15. How does PostgreSQL provide security?
PostgreSQL employs two tiers of security.
Network-level security- Utilization of Unix Domain sockets, TCP/IP sockets, and firewalls for network-level security.
Transport-level security- Transport-level security employs SSL/TLS to ensure the safe database communication
Database-level security- Roles and permissions, row-level security (RLS), and auditing are all characteristics of database-level security.
In this article, we have seen important PostgreSQL questions. We got a good understanding of different PostgreSQL terminologies. Below are some major takeaways from the above article:
1. We have seen PostgreSQL’s tokens and what are the benefits of using PostgreSQL.
2. We learned about How to set up a PostgreSQL database?
3. We got an understanding of how we can create a table in PostgreSQL?
And much more.
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