Postgre SQL Interview Questions
Looking for the Postgre SQL Interview Questions? Your research ends up here. Here are Top 10 Important Postgre SQL Interview Questions, which can help you to develop your Point to Point Skills in any Postgre SQL Specialized interview.
Top 10 Important Postgre SQL Interview Questions
Q1.What are the main features of PostgreSQL?
Following are some of the features of PostgreSQL
- Object-relational database.
- Support and extensibility for SQL.
- Flexible API and database validation.
- MVCC and procedural languages,
- WAL and Client Server.
Q2.What is Cube Root Operator (||/) in PostgreSQL?
Returns Cube Root of a number
e.g. : Select ||/ 16 “Cube Root of 16”
Q3.Provide a brief explanation of the functions in PostgreSQL?
Functions are an important part because they help in executing the code on the server. Some of the languages to program functions are PL/pgSQL, a native language of PostgreSQL, and other scripting languages like Perl, Python, PHP etc. statistical language named PL/R can also be used to increase the efficiency of the functions.
Q4.Can you explain pgadmin?
Pgadmin is a feature that is known to form a graphical front-end administration tool. This feature is available under free software released under Artistic License. Pgadmin iii is the new database administration tool released under artistic license.
Q5.What is Multi-version control?
Multi-version concurrency control or MVCC is used to avoid unnecessary locking of the database. This removes the time lag for the user to log into his database. This feature or time lag occurs when someone else is accessing the content. All transactions are kept as a record.
Q6.What will be new characteristics of PostgreSQL 9.1?
During the process of updating the project, one can never be certain that features will go in and which ones won’t make the cut. The project has precise and stringent standards for quality and some patches may or may not match them before the set deadline.
Currently, the 9.1 version is working on some important features which include JSON support, synchronous replication, nearest-neighbor geographic searches, collation at the column level, SQL/MED external data connections, security labels as well as index-only access. However, this list has a high chance of changing completely by the time Postgre 9.1 is released.
Q7.What is command enable-debug?
The command enable-debug is used to enable the compilation of all the applications and libraries. The execution of this procedure usually impedes the system, but it also amplifies the binary file size. Debugging symbols which are present generally assist the developers in spotting the bugs and other problems which may arise associated with their script.
Q8.What are the indices of PostgreSQL?
These are inbuilt functions or methods like GIST Indices, hash table and B-tree which can be used by the user to scan the index in a backward manner. Users can also define their indices of PostgreSQL.
Postgre SQL Official Website for Training and Downloads.
Q9.What is the option in PostgreSQL to check rows that are affected in a previous part of the transaction?
The SQL standard is defined by four levels of transaction isolation basically regarding three phenomena. The three phenomenon must be prevented between concurrent transactions. The unwanted phenomenon is
- Phantom read: a transaction that re-executes a query, returning a set of rows that satisfy a search condition and then finds that the set of rows that have been satisfying the condition has changed due to other recently committed transaction.
- Non-repeatable read: a transaction that re-reads the data that it has previously read then finds that data has already been modified by another transaction.
- Dirty reads: a transaction when reads data that is written by a concurrent uncommitted transaction is the dirty read.
Q10.What do you mean by CTID?
CTIDs is a field, which exists in every PostgreSQL table and is known to identify specific physical rows according to their block and offset positions within a particular table. They are used by index entries to point to physical rows.
It is unique for each record in the table and easily denotes the location of a tuple. A logical row’s CTID changes when it is updated, so the CTID cannot be used as a long-term row identifier. However, it is sometimes useful to identify a row within a transaction when no competing update is expected.