Interview Questions.

Question 1. What Is Postgresql?

Answer :

This is regarded as one of the most a success open source database in the global. This is also used to create advanced applications. This is predicated on Object relational database control device. Familiarity with UNIX and Linux can be an delivered advantage at the same time as the usage of PostgreSQL.

Question 2. State Some Of The Advanced Features Of Postgresql?

Answer :

These are the following features which can be present in PostgreSQL they're

1) Object relational database
2) Extensibility and help for SQL
3) Database validation and bendy API
4) Procedural languages and MVCC
five) Client server and WAL.

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Question 3. Explain About Write Ahead Logging?

Answer :

This characteristic increases the reliability of the database by using logging adjustments earlier than any adjustments or updations to the information base. This provides log of database incase of a database crash. This helps to begin the paintings from the point it changed into discontinued.

Question four. Explain About Multi Version Concurrency Control?

Answer :

Multi model concurrency manipulate or MVCC is used to keep away from useless locking of the database. This removes the time lag for the user to log into his database. This function or time lag takes place whilst a few one else is at the content. All the transactions are kept as a report.

MySQL Tutorial
Question 5. How To Start The Database Server?

Answer :

/usr/nearby/and so forth/rc.D/010.Pgsql.Sh begin
/usr/neighborhood/etc/rc.D/postgresql begin
MySQL Interview Questions
Question 6. How To Stop The Database Server?

Answer :

/usr/nearby/and so on/rc.D/010.Pgsql.Sh forestall
/usr/neighborhood/and many others/rc.D/postgresql stop
Question 7. How To Check Whether Postgresql Server Is Up And Running?

Answer :

/usr/nearby/etc/rc.D/010.Pgsql.Sh reputation
/usr/neighborhood/and many others/rc.D/postgresql popularity?
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Question eight. What Are The Languages Which Postgresql Supports?

Answer :

Some of the languages which PostgreSQL supports are as follows:
It supports a language of its own referred to as PL/pgSQL and it helps inner procedural languages. Pl/pgSQL can be as compared to oracle, PL/SQL, and so on. Languages along with Perl, Python, TCL can be used as embedded languages.

Question 9. Explain About The Command Enable Debug?

Answer :

This command is used for allowing compilation of all libraries and packages. This technique typically slows down the device and it also will increase the binary file size. Debugging symbols are present that can help developers in noticing bugs and issues associated with their script.

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Question 10. Explain About Functions In Postgresql?

Answer :

Functions are essential because they assist the code to be finished on the server. Some of the languages that can software capabilities for green use are PL/pgSQL that is the local language of PostgreSQL. Scripting languages are supported via many languages such as PHP, Perl, Python, and so forth. PL/R a statistical language also can be used.

Question 11. Explain About Indices Of Postgresql?

Answer :

There are constructed in capabilities consisting of B-tree, hash table, and GIST indices can be used or users can outline their personal indices. PostgreSQL can test the index backwards. Expression index could be created with the end result of an expression. Partial index created with addition of WHERE clause.

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Question 12. Explain About Triggers?

Answer :

By SQL question you can cause an occasion. Triggers can be activated with the assist of INSERT and UPDATE queries. These may be attached to tables. Triggers multiple may be brought about alphabetically. These triggers have the functionality to invoke capabilities from different languages.

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Question thirteen. What Are The Different Data Types Supported By Postgresql?

Answer :

There are distinct facts types which are supported they're: 

1) Arbitrary precision numeric’s
2) Geometric primitives
3) Arrays
4) XML etc
Users can create their very own indexes and cause them to listed.

Question 14. Explain About Database Administration Tools?

Answer :

There are diverse records administration equipment they're

1) Psql
2) Pgadmin
3) Phppgadmin

Most of those gear are the front stop administration tools and net primarily based interfaces. Out of these phppgadmin is the most famous one.

Question 15. Explain About Pgadmin?

Answer :

Pgadmin forms a graphical front give up management tool. This feature is available beneath loose software program launched underneath Artistic License. Pgadmin iii is the brand new database administration tool released underneath inventive license.

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Question 16. How Do You Create A Data Base With Postgresql?

Answer :

Creating a database is the primary step in growing a database. A command $createdb newdatabasedb

CREATE DATABASE

This creates a new database and a message presentations CREATE DATABASE which indicates that the advent of the database became a success.

Question 17. What Are The Various Enhancements To The Straight Relational Data Model By Postgresql?

Answer :

There are diverse upgrades supplied to the straight relational statistics model via postgre SQl they're aid for arrays which includes a couple of values, inheritance, features and extensibility. Jargon differs due to its object orientated nature in which tables are called as classes.

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Question 18. Explain About Tokens?

Answer :

Tokens also are recognized to contain several special character symbols. It may be considered as key-word, consistent, identifier and quoted identifier. Keywords encompass pre described SQL meanings and SQL instructions. Variable names together with tables, columns, and many others are represented through identifiers.

MySQL Interview Questions
Question 19. Explain About String Constants?

Answer :

String consistent consists of a chain of characters sure by using unmarried prices. This feature is used during insertion of a individual or passing character to database objects. PostgreSQL allows the use of unmarried rates but embedded through a C style backslash. This characteristic is crucial in parsing facts.

Question 20. What Is Write Ahead Log?

Answer :

write-in advance log (WAL),  means it constantly writes the transactions to the log following with writing the changed pages to the disk to hold the transaction ACID residences.

Question 21. How To Created A Database?

Answer :

/usr/nearby/bin/createdb mydatabase

Question 22. How To List The Number Of Database?

Answer :

su -l pgsql
psql -l

Question 23. How To Take Backup Of Database?

Answer :

/usr/local/bin/pg_dump mydatabase > mydatabase.Pgdump

Question 24. How To Create A Postgresql User?

Answer :

CREATE USER user WITH password ‘password’;

MYSQL DBA Interview Questions
Question 25. What Is A Sequence?

Answer :

A sequence is a unique sort of database item designed for generating unique numeric identifiers. It is typically used to generate artificial number one keys.
Sequences are similar, but now not equal, to the AUTO_INCREMENT concept in MySQL.

Question 26. What Is A Ctid?

Answer :

CTIDs become aware of specific physical rows by their block and offset positions within a desk. They are utilized by index entries to point to physical rows. A logical row's CTID modifications when it's miles updated, so the CTID can't be used as an extended-term row identifier. But it's miles from time to time beneficial to become aware of a row within a transaction whilst no competing replace is anticipated.

Question 27. Why Do I Get The Error "errors: Memory Exhausted In Allocsetalloc()"?

Answer :

You possibly have run out of digital reminiscence for your machine, or your kernel has a low limit for positive sources. Try this before starting the server:

ulimit -d 262144
restrict datasize 256m

Java Developer Interview Questions
Question 28. How Do I Tell What Postgresql Version I Am Running?

Answer :

Run this query: SELECT model();

Question 29. How Do I Create A Column That Will Default To The Current Time?

Answer :

Use CURRENT_TIMESTAMP:
CREATE TABLE take a look at (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );

Question 30. How Do I Perform An Outer Join?

Answer :

PostgreSQL helps outer joins the usage of the SQL wellknown syntax. Here are  examples:

SELECT * FROM t1 LEFT OUTER JOIN t2 ON (t1.Col = t2.Col);
or
SELECT * FROM t1 LEFT OUTER JOIN t2 USING (col);

Question 31. How Do I Perform Queries Using Multiple Databases?

Answer :

There is not any way to question a database apart from the cutting-edge one. Because PostgreSQL hundreds database-particular device catalogs, it's far uncertain how a pass-database question should even behave.
Contrib/dblink lets in pass-database queries the usage of characteristic calls. Of route, a consumer can also make simultaneous connections to exceptional databases and merge the effects at the consumer side.

Question 32. Is Possible To Create A Shared-storage Postgresql Server Cluster?

Answer :

PostgreSQL does not guide clustering using shared garage on a SAN, SCSI backplane, iSCSI quantity, or other shared media. Such "RAC-style" clustering is not supported. Only replication-based clustering is presently supported.

Question 33. Does Postgresql Have Stored Procedures?

Answer :

PostgreSQL does not.

Oracle MySQL five.6 Database Administrator Interview Questions
Question 34. How To Pronounce Postgresql?

Answer :

publish-GRES-que-ell, per this audio document. Many people, but, simply say “publish-GRES”.

Question 35. What Are New Features Postgre nine.1?

Answer :

As usually, we can’t be positive what will pass in and what gained’t; the project has strict exceptional standards that no longer all patches could make earlier than closing date. All we will let you know is what’s being worked on, which incorporates: synchronous replication, JSON guide, security labels, nearest-neighbor geographic searches, SQL/MED external records connections, column-degree collations, and index-only get right of entry to. By the time nine.1 is launched, although, this feature listing may have changed considerably.

Question 36. Does Postgresql Run On The Cloud?

Answer :

Yes. Like different open supply databases, PostgreSQL is simple to run in digital containers and is surprisingly transportable. Several companies have guide for PostgreSQL in cloud web hosting environments, such as Heroku, GoGrid and Joyent.

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Question 37. How Does Postgresql Compare To “nosql”?

Answer :

The term “NoSQL” covers the sort of various array of non-relational database implementations … from tiny embedded databases like TokyoCabinet to massive clustered information processing structures like Hadoop … that it’s impossible to comment on them as a general elegance. Non-relational databases preceded relational databases and feature existed along them for 40 years, so deciding on between relational and nonrelational databases is nothing new. Users need to pick the database whose capabilities, implementation, and network guide their modern utility desires. Further, the use of more than one exceptional databases for huge initiatives is speedy becoming the norm, and PostgreSQL customers aren't any exception.

Question 38. How Does Postgresql Compare To Oracle/db2/ms Sql Server/informix?

Answer :

Our characteristic set is generally considered to be very competitive with other leading SQL RDBMSes. Certainly there are functions a number of them have which we don’t, and the opposite is also authentic. To date, only some benchmarks were published displaying PostgreSQL to be inside 10-30% of proprietary competition. However, we've got had many users migrate from different database systems � usually Oracle and Informix � and they're completely happy with the overall performance of their PostgreSQL systems.

Question 39. How Does Postgresql Compare To Mysql?

Answer :

This is a subject which can begin several hours of discussion. As a short summary, MySQL is the “clean-to-use, internet developer” database, and PostgreSQL is the “characteristic-rich, standards-compliant” database. PostgreSQL is liberally certified and owned by its network; MySQL is GPL-licensed and owned by means of Oracle. Beyond that, every database user ought to make his own evaluation; open supply software program makes doing comparisons very easy.

Question 40. Explain About Concurrency With The Help Of Mvcc?

Answer :

Multi model concurrency manage is used to manage concurrency. This function may be very useful due to the fact modifications made inside the database will not be visible to different users until the transaction is finished. This eliminates the want for examine locks. ACID principles are given a similarly raise with the aid of this option and may be carried out in wellknown.

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