UpWork (oDesk) & Elance PostgreSQL RDBMS Test Question & Answers

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Ques : Which authentication methods are supported by PostgreSQL?
Ans  :  Trust
        PAM
        LDAP
        Radius
        Password

Ques : Which index types are supported by PostgreSQL?
Ans  :  B-tree
        GiST
        Hash
        GIN

Ques : Out of the following backup approaches, which ones are applicable to PostgreSQL?
Ans  : SQL dump
       File system level backup
   Continuous archiving

Ques : In the following operation, which ones can trigger a trigger?
Ans  : insert
       update
   delete

Ques : Which index types support multicolumn indexes?
Ans  : B-tree
       GiST
   GIN

Ques : What kind of triggers are offered by PostgreSQL?
Ans  : Per-row triggers
      Per-statement triggers

Ques : Which of the following statements will cast the integer value 1 to type text?
Ans  :  SELECT CAST(1, text) as cast_integer;
        SELECT 1::text AS cast_integer;
 
Ques : Are the contents of the pg_autovacuum system catalog saved when pg_dumpall is used to backup the database?
Ans  : No

Ques : Can deferrable constraints be deferred by a trigger?
Ans  : Yes

Ques : After a PostgreSQL installation, how will you create the database cluster?
Ans  :  With initd

Ques : Consider the following query:

Create table foo (bar varchar);

What will be the size limit of the bar?
Ans  :  No limit (It will be equivalent to the text)

Ques : What is the difference between to_tsvector() and ::tsvector ?
Ans  :  to_tsvector () can be used in select statements, while ::tsvector cannot

Ques : While creating a trigger, the function it will call may be created after it and attached to it.
Ans  : True

Ques :  What is the command used to import a backup made with pg_dumpall > file.dmp?
Ans  :  psql -f file.dmp

Ques : An ISO-8601 time may be entered into a table using the numeric format 012411 instead of 01:24:11.
Ans  : True

Ques : Consider the following empty table:

CREATE TABLE example (
    a integer,
    b integer,
    c integer,
    UNIQUE (a, c)
);

Which of the following inserts will cause an error?
Ans  : insert into example (a, b, c) values (1, 2, 3), (1, 4, 3);

Ques : What is the effect of turning fsync off in postgresql.conf?
Ans  : File synchronization will be deactivated

Ques : What is the ~ operator?
Ans  : POSIX regular expression match operator

Ques : What is the default ordering when ORDER BY is not specified?
Ans  : The ordering is unknown if not specified

Ques : Which one of the following text search functions does not exist?
Ans  :  plainto_tsvecto

Ques : Which PostgreSQL version added the enum datatype?
Ans  : 8.0

Ques :  While creating a table with a field of the serial type, a sequence will be created.
Ans  :  True

Ques : What can be stored in a column of type decimal(4,3)?
Ans  : 4 numeric values with up to 3 digits to the right of the decimal point.

Ques : What interfaces are available in the base distribution of PostgreSQL?
Ans  : C

Ques : A table can have only one primary key column.
Ans  : True

Ques : What command will correctly restore a backup made with the following command?
pg_dump -Fc dbname > filename
Ans  : psql -f filename dbname

Ques :   How can you configure PostgreSQL autovacuum?
Ans  : By editing postgresql.conf

Ques :  What library is used by PostgreSQL for encryption?
Ans  : None of the above

Ques : On a UNIX system, what is the best way to prevent all non-local connections to the postmaster?
Ans  :  None of the above

Ques : How will you change the TCP port which PostgreSQL will listen to?
Ans  : By changing "port" in postgresql.conf

Ques : Which of the following queries will create a table with two fields, "id" and "name" with "id" as an auto incrementing primary key?
Ans  :  create table foo (id serial primary key, name varchar(255));

Ques : How will you list the available functions from psql?
Ans  :  \df

Ques : What is the well known port number for the postgresql database service?
Ans  : 5432

Ques : What is true regarding file system backup?
Ans  : All of the above

Ques : How do you alter a column to forbid null values?
Ans  : None of the above

Ques : What is the storage size of an integer on a 64bit system?
Ans  : 4bytes

Ques : Which function should be used to highlight the results?
Ans  :  ts_highlight

Ques : When using LIKE to compare strings, what is the wildcard operator (operator which matches zero or more characters)?
Ans  : *

Ques : For proper results, which of the following should contain a tsvector?
Ans  : Lexemes

Ques : Which of the following statements will produce an error?
Ans  :  SELECT now()::int;

Ques : To backup a database, the postmaster daemon must be halted.
Ans  : True

Ques : The following statement will retrieve the second element of the array column products in table store_products.

SELECT products[1] FROM store_products;
Ans  : True

Ques : SELECT 'infinity'::timestamp;

Will this statement produce an error?
Ans  : Yes

Ques :  What is the difference between tokens and lexemes?
Ans  :  A lexeme is a string while a token is an intege

Ques : Which kind of index can be declared unique?
Ans  : Hash

Ques :  SELECT rtrim('foobar', 'abr');

The result of this statement is foo.
Ans  : True

Ques : SELECT !!3;

What output will this statement give?
Answers:
Ans  : 6

Ques : How do you create a table with a field of the int array type?
Ans  : create table foo (bar integer[]);

Ques : create table foo (bar integer[]);
Ans  : None of the above

Ques : Which of the following statements will create a table with a multidimensional array as second column?
Ans  : CREATE TABLE favorite_books (customer_id integer, themes_and_titles text[][]);

Ques : If max_connections is 10 and 10 connections are currently active, how can you be sure the superuser will be available to connect?
Ans  :  Set superuser_reserved_connections in postgresql.conf

Ques : How will you rank text search results?
Ans  : With the ORDER BY operator

Ques : Which of the following statements will create a table special_products which is a child of the table store_products?
Ans  : CREATE TABLE special_products (quality int) INHERITS store_products;

Ques : Which of the following statements will create a table?
Ans  : SELECT * INTO products_backup FROM special_products;

Ques : Which of the following statements will retrieve the number of values stored in an array column?
Ans  : SELECT array_dims(products) FROM store_products;

Ques : Does PostgreSQL support SSL?
Ans  : Yes

Ques : Given a table special_products that inherits from a table store_products, which of the following statements will modify store_products only without affecting its child table?
Ans  : UPDATE ONLY store_products SET name = 'Wine' WHERE id = 2;

Ques : How do you select a single random row from a table?
Ans  : SELECT * FROM tab ORDER BY random() LIMIT 1;

Ques : PostgreSQL triggers can be written in C directly.
Ans  : True

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