SQL

Question 1

What does SQL stand for?

Answer 1

Structured Query Language

Question 2

What type of language is SQL?

Answer 2

Declarative language

Question 3

What are the four main commands in SQL?

Answer 3

• SELECT
• UPDATE
• INSERT
• DELETE

Question 4

What is the purpose of the SELECT command in SQL?

Answer 4

Used for retrieving data from a database table

Question 5

What is the general form of the SELECT command?

Answer 5

SELECT <attribute> FROM <table> WHERE <condition> ORDER BY <ASC/DESC></condition></attribute>

Question 6

Is the ORDER BY clause mandatory in a SELECT command?

Answer 6

No, it is optional

Question 7

What is the purpose of the UPDATE command?

Answer 7

Used for modifying the attributes of an existing entity

Question 8

What is the general form of the UPDATE command?

Answer 8

UPDATE <table> SET <attribute> = <value> WHERE <attribute> = <value></value></attribute></value></attribute>

Question 9

What is the purpose of the DELETE command?

Answer 9

Used for removing entities from a database

Question 10

What is the general form of the DELETE command?

Answer 10

DELETE FROM <table> WHERE <condition></condition>

Question 11

What is the purpose of the INSERT command?

Answer 11

Used to add new records to an existing table

Question 12

What is the general form of the INSERT command?

Answer 12

INSERT INTO <table> (<column1>, <column2>, …) VALUES (<value1>, <value2>, …)</value2></value1></column2></column1>

Question 13

How can the INSERT command be simplified?

Answer 13

INSERT INTO <table> VALUES (<value1>, <value2>, …) when all columns are used in correct order</value2></value1>

Question 14

What are wildcards in SQL?

Answer 14

Used to specify any possible value

Question 15

How are wildcards typically notated in SQL?

Answer 15

With an asterisk (*)

Question 16

What command is used to create a new database table in SQL?

Answer 16

CREATE command

Question 17

What does the CREATE command specify?

Answer 17

• Name of the new table
• Attributes and their data types
• Entity identifiers like primary and secondary keys

Question 18

What does the CREATE command do?

Answer 18

Creates an empty table

Question 19

What is the CHAR data type in SQL?

Answer 19

A fixed-length string with a specified number of characters

Question 20

What is the VARCHAR data type in SQL?

Answer 20

A variable-length string with a maximum specified number of characters

Question 21

What is the INT data type in SQL?

Answer 21

An integer stored using a specified number of bits

Question 22

What does the FLOAT data type represent?

Answer 22

A number with a fractional part stored with specified bits and precision

Question 23

What format is the DATE data type in SQL?

Answer 23

YYYY-MM-DD

Question 24

What is the format of the DATETIME data type in SQL?

Answer 24

YYYY-MM-DD HH:MM:SS

Question 25

What format does the TIME data type use?

Answer 25

HH:MM:SS

Question 26

What does the YEAR data type store?

Answer 26

A year in YY or YYYY format

Question 27

What is the function of client-server databases?

Answer 27

Provide simultaneous access to a database for multiple clients

Question 28

What problem can occur with concurrent access in databases?

Answer 28

Database updates being lost if two users edit a record at the same time

Question 29

What methods can manage concurrent access in databases?

Answer 29

* Record locks * Serialisation * Timestamp ordering * Commitment ordering

Question 30

What is a record lock?

Answer 30

Locks a record for one user, blocking others until it is unlocked

Question 31

What is serialisation in database access management?

Answer 31

Queues requests from users instead of locking a field

Question 32

What is timestamp ordering?

Answer 32

Commands are executed based on the order of their timestamps

Question 33

What is commitment ordering?

Answer 33

An algorithm determines the optimal order to execute commands based on impact