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.
|Quick Questions about PostgreSQL|
|What is PostgreSQL?||It is a free and open-source relational database management machine emphasizing extensibility. It is designed to deal with a range of workloads, from single machines to records warehouses or Web offerings with many concurrent users.|
|What is the Latest Version of PostgreSQL?||12.1 released on 14th November 2019|
|When was PostgreSQL Initial released?||8th July 1996|
|What language does PostgreSQL use?||C Language|
|Who developed PostgreSQL?||Michael Stonebraker|
|What operating system use PostgreSQL?||Windows, Linux, macOS, OpenBSD|
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
|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 provides several index types like Hash, B-tree, SP-GiST, BRIN, and GIN. All these types uses a seprate algorithm that is best suited to queries.
In terms of learning databases, MySQL is perfect. It is the first choice for web-based projects merely requiring a database for transactions and nothing else. But, PostgreSQL is better in terms of functionalities and performance. It is more used in the execution of complex queries, data warehousing, and data analysis.
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.
Multi-Version Concurrency Control (MVCC) is an advanced method used in PostgreSQL for improving the performance of a database in a multi-user environment. Unlike lock models in other databases, PostgreSQL uses a multi-version environment in which locks that are acquired for reading data don’t conflict with locks acquired for writing the data. Hence, making the process more compartmentalized and a lot faster.
|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).
|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 TABLE users
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.
|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.|
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.
Indexes are special lookup tables that are used by the database search engine to speed up data retrieval. Simply defining, an index is a pointer to a specific data in a table.
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.
PgAdmin is a free, open-source PostgreSQL database administration GUI that is used in Microsoft Windows, Mac OS X, and Linux systems. PgAdmin is used for database server information retrieval, development process, Quality testing, and other ongoing maintenance.
Follow these steps to install PgAdmin:
- Launch pgAdmin 4.
- Go to the “Dashboard” tab, click on the “Quick Link” section and then click on “Add new Server”
- Now, select the “Connection” tab in the “Create-Server” window.
- Now, configure the connection as follows:
- Enter your server's IP address in the “Hostname/Address” field.
- Specify the “Port” as “5432”.
PostgreSQL stores its transaction logs in the following location
pg_wal folder of the data directory (Note: previous versions of PostgreSQL used a folder called pg_xlog – this folder was renamed in version 10 to increase the importance of the file within).
Follow these steps to successfully create a database in PostgreSQL using PgAdmin:
- Log into PostgreSQL using pgAdmin
- Now, go to the Databases section and right-click on it
- Now, enter the database name, owner and configure parameters and press OK after it is done.
Follow these steps to carefully change the user password Postgres in Laravel:
- Step 1: Make yourself the “Postgres” system user (through the root user, sudo or via SSH public key verification)
- Step 2: Connect to the local server using “PSQL”
- Step 3: Type this meta-command of PSQL \password
It should look something like this:
A sequence in PostgreSQL is a special form of data that is created to generate multiple numeric identifiers in the PostgreSQL database. It is most often used to create sequences and artificial primary keys similar to Auto_Increment in MySQL. The basic role of sequences in PostgreSQL is to create unique identifiers between multiple rows inside a table.
The simplest way to check whether your server in PostgreSQL is running or not:
ps auxwww | grep postgres
In versions other than 8.3 you need to run this command
/Library/PostgreSQL/8.3/bin/postgres -D /Library/PostgreSQL/8.3/data
PgAdmin comes with built-in support to debug your Pl/PgSQL codes. However, in order to enable this, you need to compile and install a separate plug-in for PostgreSQL
Now, once you have set up a proper environment for debugging, go to edit
/etc/postgresql/9.4/main/postgresql.conf and enable the debugger plugin.
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