PostgreSQL Interview Questions

Last update: 09 Jan 2020, 36 QuestionsAsk Question
A Quick Overview of PostgreSQL
PostgreSQL Interview Questions

PostgreSQL is one of the most advanced, object-relational database management systems and open-source developed by PostgreSQL Global Development Group at Berkeley Computer Science Department, University of California. With its strong hand on proven data integrity, reliability, architecture, extensibility and excellent feature set, PostgreSQL has earned the prominence of being a superior and robust solution globally, thus highly increasing the employment base for this niche. We are going to discuss the most interviewer asked PostgreSQL interview questions for the acknowledgment of future aspirants in this niche.

With the operation freedom of all major operating systems including UNIX, Windows, Linux, and Mac OS X; PostgreSQL supports images, text, video as well as sound, and includes programming interfaces for C, C++, Perl, Java, Tcl, Ruby, and Open Database Connectivity.

What is PostgreSQL? PostgreSQL, also acknowledged as Postgres, is a free and open-source relational database management machine emphasizing extensibility and technical requirements compliance. It is designed to deal with a range of workloads, from single machines to records warehouses or Web offerings with many concurrent users.
Latest Version 12.1 released on 14th November 2019
Initial release date 8th July 1996
Written in C Language
Operating system Windows, Linux, macOS, OpenBSD
License: PostgreSQL License

Best PostgreSQL Interview Questions And Answers

It’s a general purposed and advance object-relational database management system used to add custom functions developed using a various programming language such as C, C++, Java, etc. Designed to be extensible, PostgreSQL implements MVCC or multi-version concurrency control.

PostgreSQL has many exciting features added to it. Here are a few of them:

  • By protecting data integrity, users can build a fault-tolerant environment.
  • Easy compatibility with significant platforms, languages, and middleware.
  • Multi-version concurrency control is supported.
  • The client-server network architecture is supported.
  • Trigger-based and log-based replication SSL
  • High availability and standby server
S.no PostgreSQL MySQL
1. PostgreSQL is open-source software. MySQL has several paid editions.
2. It is ACID compliant from the ground up. It is only ACID compliant when suing NDB and InnoDB Cluster Storage engines.
3. Largely SQL compliant Partially compliant to some of the SQL versions
4. Used for large systems where to write and read speeds are crucial, and data need to be validated. Used for web-based projects that require a database for data transaction

PostgreSQL supports various data types, which includes:

  • Boolean
  • Numeric types
  • Character types
  • Temporal types
  • Array
  • UUID
  • JSON
  • store
  • Special types such as geometric data and particular types

In PostgreSQL, the DUAL table is a special one-column, one-row table present by default. It is created as a view to easing porting problems, which allows code to remain compatible with Oracle SQL without obstructing the Postgres parser.

PostgreSQL has no maximum database size, so users can put unlimited data into it. But, the table, row, and field size are limited. The row and indexes are also universal for its users.

PostgreSQL usually stores its desk facts in chunks of 8KB. The quantity of these blocks is confined to a 32-bit signed integer, giving the most desk dimension of 16TB.

The Multi-Version Concurrency Control or MVCC is a method present in PostgreSQL to handle data consistency when multiple processes are accessing a single table. It is a standard database technique and not limited only to PostgreSQL.

S.no PostgreSQL MongoDB
1. It’s an object-relational database management system. It uses JSON-like documents to store schema-free data.
2. uses tables, triggers, constraints, roles, stored procedures and views as the core components Uses Key, Collection, Document, and Value.

A token can be a keyword, an identifier, a quoted identifier, a literal (or constant), or a distinctive personality symbol. Tokens are generally separated with the aid of whitespace (space, tab, newline), however, need not be if there is no ambiguity (which is usually only the case if an exceptional persona is adjoining to some other token type).

S.no Oracle PostgreSQL
1. Mostly aid object-relational database management system open source object-relational database management system
2. The implementation language is C. Implementation language is C and C++.
3. Server operating systems here are OS X, Linux, Windows, z/OS, AIX, and HP-UX. Server operating systems here are HP-UX, NetBSD, Solaris, Windows, Unix, Linux, and FreeBSD.
4. More database productivity Less database productivity
5. Advance security options Good security support but less compared to Oracle
  • Download Windows PostgreSQL one-click the installer and run it.
  • Choose to install PostgreSQL as a Windows Service.
  • If needed, change the installation directory and click next
  • Choose the components you want to install & click next
  • If needed, change the data location
  • Enter the user password and if necessary make a note of it.
  • Let the port number by the default
  • Once the installation is complete, uncheck the Stack Builder prompt and click finish
  • Now go to start menu, search and start pgAdmin 4
  • Click on servers present on the pgAdmin homepage and choose Postgre SQL 10
  • Enter the superuser password, and the dashboard will begin for your use

As the default repositories of Ubuntu contain Postgres packages, we can install it easily using the apt packaging system. Refresh the local package index and then install the Postgres packages and a -contrib package which adds additional functionality and utilities. The PostgreSQL software installation process is finished now.

To change the records type of a column, you use the ALTER TABLE assertion as follows:

ALTER COLUMN username[SET DATA] TYPE new_data_type;

The ctid field exists in every PostgreSQL table. It is unique for every record in a table and denotes the turple location. It can be used to delete records. The thing to remember, we should only use ctid if we have absolutely no other unique identifier to use.

In PostgreSQL, table partitioning refers to splitting a large table into smaller sections. PostgreSQL supports list and range partitioning via table heritance. Users have to create each partition as a child table of the master table.

Even though PostgreSQL has unlimited database size for users, but it has a limit for maximum table size. The maximum table size is set to 32 TB.

S.no PostgreSQL SQLServer
1. Microsoft’s relational DBMS Widely used open source object-relational database management system
2. Implementation language is C. The implementation language is C++.
3. Supports server is operating systems such as HP-UX, NetBSD, Solaris, Windows, Unix, Linux, and FreeBSD. Supports only Linux and Windows.
4. Doesn’t has the in-memory capability. Has in-memory capability.

An explicit 'vacuum' call is made to update statistics in PostgreSQL. Users can also use the Analyze to perform so.

In PostgreSQL, the index is a common way for database performance enhancement. It allows the database server to find the retrieve specific rows faster compared to without index. It also adds overhead to the database system as a whole, so users have to implement them sensibly.

You can use pg_ctl -D "C:\Program Files\PostgreSQL\9.6\data" start to start PostgreSQL on Windows.

First, you want to find the PostgreSQL database directory, it can be something like C:\Program Files\PostgreSQL\10.4\data. Then open Command Prompt and execute this command. Now use pg_ctl -D "C:\Program Files\PostgreSQL\9.6\data" stop to stop these service.

Now, let’s discuss an advanced set of PostgreSQL dba interview questions further above for candidates searching for a near-future job change or going to start their career from the ground level.


  • Enterprise-class functions and performance with an open-source database management system with unlimited development possibilities.
  • Superior development possibility with diverse community purposed modules.
  • Store Procedure functions can be used for a server environment.
  • It offers diverse indexing techniques.
  • Availability of full-text search
  • Diverse extension functions and replications
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