PostgreSQL MCQ
PostgreSQL MCQ : This PostgreSQL Beginner Quiz contains set of 60 PostgreSQL Quiz which will help to clear any Mcqs exam which is designed for Beginner.
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1) Which command is used to the list of databases?
- \d
- \l
- \db
- \ld
2) which command is used to connect/select a database
- \l <dbnam>
- \cd <dbname>
- \s <dbname>
- \c <dbname>
3) Which command list down all the tables in an attached database.
- \db
- \c
- \d
- \l
4) \d tablename command
- lists the table
- lists all the tables in the database
- describes the structure of the table
- this is not a valid command
5) A_________ is a named collection of tables.
- database
- table
- macro
- schema
6) which statement about the where clause is true?
- WHERE clause is used to specify a condition while fetching the data
- it returns only the records that’s satisfies the condition
- WHERE clause can be used in UPDATE and DELETE statements
- All of the Above
7) what does the following query do? SELECT * FROM CUSTOMER LIMIT 3 OFFSET 2;
- picks up three records
- picks up three records starting from the second position
- picks up second and third record
- throws an error
8) which command is used to list indexes available on CUSTOMER table
- \show CUSTOMER
- \indexes CUSTOMER
- \i CUSTOMER
- \d CUSTOMER
9) which command is used to select the customer who has been spending more than 200
- SELECT customer_id, SUM (amount) FROM payment GROUP BY customer_id WHERE amount > 200;
- SELECT customer_id, SUM (amount) FROM payment GROUP BY customer_id WHERE SUM (amount) > 200;
- SELECT customer_id, SUM (amount) FROM payment GROUP BY customer_id WHERE SUM (amount) > 200;
- SELECT customer_id, SUM (amount) FROM payment GROUP BY customer_id HAVING amount > 200;
10) Which operator performs pattern matching?
- Like
- Between
- In
- Exists
11) What type of join is used when you want to use a join between columns that are in the same table?
- SELF
- EQUI
- OUTER
- CROSS
12) The basic psql command to list tables is?
- \dT
- \dt
- \do
- \h
13) The most common method to get data into a table is to use what command?
- Write
- Insert
- Execute
- Send
14) PostgreSQL is
- a relational database management system.
- a hierarchical database management system.
- a network-type database management system.
- an XML database management system.
15) PostgreSQL runs on
- all major operating systems, including Linux, UNIX (AIX, BSD, HP-UX, SGI IRIX, Mac OS X, Solaris, Tru64), and Windows.
- on all UNIX versions except Solaris.
- Linux and Windows only.
- Windows only
16) What command tells PostgreSQL that all of the changes you made to a database should become permanent?
- Apply
- Execute
- Commit
- Send
17) ____________ allow us to define formally in the database how different tables relate to each other.
- Views
- Temporary tables
- Foreign key constraints
- Table management
18) If you don’t specify ASC or DESC, PostgreSQL will assume you want to see results:
- in ascending order
- grouped together by field type
- in a random order
- in descending order
19) The value NULL, in database terminology, means?
- The value is undetermined at this time
- The value is undetermined
- The value is not relevant for this particular row.
- All of the Above
20) What does the following statement do? CREATE INDEX lower_title_idx ON books ((lower(title)));
- Modifies an index in place to be lowercase
- Creates a new index with a special operator class ‘lower’ for case insensitive comparisons
- Creates an index for efficient case-insensitive searches on the titles column within the books table
- Nothing, it’s invalid SQL
21) which command is used to supress the duplicate records?
- distinct
- duplicate
- supress
- hide
22) Which of the following is not true about inserting news rows to a table?
- INSERT statement is use for inserting new rows into the table
- You cannot insert rows with NULL values in a table
- you many insert a new row containing values for each column
- you can ignore sore columns while insertuing the rows in a table
23) which of the following command is used o modify a SEQUNCE
- ALTER SEQUENCE
- SELECT SEQUENCE
- DROP SEQUENCE
- MODIFY SEQUENCE
24) what is returned by ROUND(789.8379,2)?
- 84
- 83
- 78
- 789
25) which of the following is not true about creating CONSTRAINTS?
- constraints are defined using CREATE CONSTRAINT command
- they are created at the same time when table is created
- they should be created after the table is created
- all the constrains are stored in data dict
26) which of the following is true about Cartesian product?
- is formed when a join condition is ommited
- A Cartesian product is formed when a join condition is valid.
- Some rows in the first table are joined to all rows in the second table
- All rows in the first table are joined to some rows in the second table.
27) Which of the following is true about a group function?
- Group functions operate on set of rows to produce multiple results per group
- Group functions ignore NULL values
- DISTINCT keyword makes a group function consider duplicate values
- None of the above
28) Which of the following is not true about the COALESCE function?
- It returns the first NON-NULL expression in the parameter list
- It takes multiple alternate values
- It returns the first value in the parameter if it is NULL
- None of the above
29) In which of the following cases a DML statement is executed?
- When a table is created
- When a Transaction is committed
- When new rows are added to a table
- None of the above
30) Consider the schema: STUDENTS(student_code, first_name, last_name) Which of the following query will display all the students where the second letter in the first_name is ‘a’ ?
- select first_name from students where first_name like ‘_a%’;
- select first_name from students where first_name like ‘%a_’;
- select first_name from students where first_name like ‘%a%’;
- select first_name from students where first_name like ‘_a_’;
31) Consider the schema: STUDENTS(student_code, first_name, last_name,email) Which of the following query would display names of all the students whose email ids are not provided?
- select first_name , last_name from students where email=0;
- select first_name , last_name from students where email=’ ‘;
- select first_name , last_name from students where email=’NULL’ ;
- select first_name , last_name from students where email is NULL
32) Which of the following is not a character manipulation function?
- CONCAT
- INSTR
- SUBSTR
- COALESCE
33) What is returned by INSTR‘WIPROLIMITED ′ , ‘P ′?
- 3
- 2
- WIPRO
- LIMITED
34) What is returned by SUBSTR(‘WIPRO LIMITED ′,1,6)
- WIPRO
- WIPROL
- IPRO L
- IPROLI
35) What is returned by SUBSTR(‘WIPRO LIMITED ′,-1,1)
- NULL
- 0
- D
- E
36) Which of the following is not a group function?
- SUM
- NVL
- COUNT
- MIN
37) Which of the following functions can be used on both numeric as well as nonnumeric data?
- SUM
- AVG
- COUNT
- VARIANCE
38) Which of the following is not true about the MAX and MIN functions?
- Both can be used for any data type.
- MAX returns the maximum value
- MIN returns the minimum value.
- Both works only with Numeric datatype
39) A subquery can be placed in which of the SQL clauses?
- The WHERE clause
- The HAVING clause
- The FROM clause
- All of the above
40) Which of the following comparison operators could be used in a multiple row query?
- IN
- ANY
- ALL
- All of the Above
41) which SQL statement is used to extract data from the table?
- OPEN
- SELECT
- GET
- EXTRACT
42) With SQL, how do you select all the records from a table named “Persons” where the value of the column “FirstName” is “Lakshmi”?
- SELECT [all] FROM Persons WHERE FirstName=’Lakshmi’
- SELECT [all] FROM Persons WHERE FirstName LIKE ‘Lakshmi’
- SELECT * FROM Persons WHERE FirstName<>’Lakshmi’
- SELECT * FROM Persons WHERE FirstName=’Lakshmi’
43) which SQL keyword is used to sort the result-set
- SORT
- ORDER
- SORT BY
- ORDER BY
44) With SQL, how can you return all the records from a table named “Persons” sorted descending by “FirstName”?
- SELECT * FROM Persons ORDER FirstName DESC
- SELECT * FROM Persons ORDER BY FirstName DESC
- SELECT * FROM Persons SORT BY ‘FirstName’ DESC
- SELECT * FROM Persons SORT ‘FirstName’ DESC
45) With SQL, how can you insert “Olsen” as the “LastName” in the “Persons” table?
- INSERT (‘Olsen’) INTO Persons (LastName)
- INSERT INTO Persons (‘Olsen’) INTO LastName
- INSERT INTO Persons (LastName) VALUES (‘Olsen’)
- INSERT INTO Persons (LastName) (‘Olsen’)
46) How can you change “Hansen” into “Nilsen” in the “LastName” column in the Persons table?
- MODIFY Persons SET LastName=’Hansen’ INTO LastName=’Nilsen
- MODIFY Persons SET LastName=’Nilsen’ WHERE LastName=’Hansen’
- UPDATE Persons SET LastName=’Hansen’ INTO LastName=’Nilsen’
- UPDATE Persons SET LastName=’Nilsen’ WHERE LastName=’Hansen’
47) With SQL, how can you delete the records where the “FirstName” is “Peter” in the Persons Table?
- DELETE FirstName=’Peter’ FROM Persons
- DELETE ROW FirstName=’Peter’ FROM Person
- DELETE FROM Persons WHERE FirstName = ‘Peter’
- DELETE FROM Persons WHERE FirstName is ‘Peter’
48) What is the most common type of join?
- INNER
- SELF
- FULL OUTER
- EXPLICIT
49) Which operator is used to select values within a range?
- RANGE
- WITHIN
- BETWEEN
- IN
50) What is True about Indexes?
- Indexes should not be used on a smaller table
- Indexes should not be created on a column that contain more of NULL values
- Indexes should not be used on a table that is updated frequently
- All of the Above
51) how to create an Index on salary column of Customer table?
- Create Index salary_index on Customer(salary)
- Create Index on Customer(salary)
- Create Index salary_index using Customer(salary)
- Create Index salary_index on salary of customer
52) What does the following statement do? CREATE INDEX lower_title_idx ON books ((lower(title)));
- Modifies an index in place to be lowercase
- Creates a new index with a special operator class ‘lower’ for case insensitive comparisons.
- Creates an index for efficient case-insensitive searches on the titles column within the books table
- Nothing, it’s invalid SQL
53) The syntax to view the indexes of an existing postgreSQL table is :
- index database_name.table_name
- \d table_name
- \i table_name
- index table_name
54) Which SQL statement is used to delete records from a table?
- DELETE
- COLLAPSE
- REMOVE
- DROP
55) CREATE vwEmployee VIEW AS SELECT * FROM Employee WHERE ID < 100 choose the correct option
- View name must be after keyword view
- replace column name instead of *
- VIEW is an optional keyword
- there is no error in the query
56) Views are also called as:
- Complex tables
- Simple tables
- Virtual tables
- Actual Tables
57) What is true about views among all the given below statements:
- View never references actual table for which it is created.
- View can’t use JOIN in it’s query.
- The performance of the view degrades if they are based on other views
- Only option to safeguard data integrity.
58) Which category Delete query exits?
- DDL
- DML
- TCL
- DQL
59) Which one is correct syntax for Where clause
- SELECT WHERE “Condition” Col1, Col2 FROM “Table” ;
- SELECT “Condition” Col1, Col2 FROM “Table” WHERE;
- SELECT Col1, Col2 FROM “Table” WHERE “condition”;
- None of the above