SQL

Question 1

What does sql stand for?

Answer 1

Structured Query Language

Question 2

What are the advantages of using SQL?

Answer 2

It’s easy to learn and use (as it’s a declarative language)

Question 3

What are the 5 main SQL commands and what are the used for?

Answer 3

CREATE - used for creating tables
SELECT - used for retrieving data from a table
UPDATE - used for changing an attribute in an existing record
INSERT - used for
DELETE - used for removing records from a table

Question 4

What is the format for a SELECT command?

Answer 4

SELECT attributes FROM table WHERE condition ORDER BY asc/desc

Question 5

What is the format for a UPDATE command?

Answer 5

UPDATE table (attributes) SET new values WHERE = condition

Question 6

What is the format for a DELETE command?

Answer 6

DELETE attributes FROM table WHERE condition

Question 7

What is the format for a INSERT command that inserts values into all columns?

Answer 7

INSERT INTO table VALUES (value1, value2, …)

Question 8

What is the format for a INSERT command that inserts values into specific columns?

Answer 8

INSERT INTO tablename (column1, column2) VALUES (value1, value2, …)

Question 9

What does SELECT * FROM …. mean and what is the special name for it?

Answer 9

• It means select all the attributes from the database that apply to the condition.
• The asterix (select all) is called a wildcard

Question 10

What is the format for a CREATE command that inserts values into specific columns?

Answer 10

CREATE TABLE  ( VARCHAR(225),   VARCHAR(255), 
  YEAR, PRIMARY KEY ( , ))

Question 11

How is a fixed length string data type represented?

Answer 11

CHAR(size) - A string with the number of

characters specified by size

Question 12

How is a variable length string data type represented?

Answer 12

VARCHAR(size) - A string with any number of characters up to the number specified by size

Question 13

How is a Integer data type represented?

Answer 13

INT(size) - Stores a whole number using the number of bits specified by size

Question 14

How is a Number with fractional part data type represented?

Answer 14

FLOAT(size, precision) - A number stored using the number of bits specified by size with digits after the decimal point up to the number specified by precision

Question 15

How is a Date data type represented?

Answer 15

DATE - A date in the format YYYY-MM-DD

Question 16

How is a Date and time data type represented?

Answer 16

DATETIME - A date and time combined in the format YYYY-MM-DD HH:MM:SS

Question 17

How is a Time data type represented?

Answer 17

TIME - A time in the format HH:MM:SS

Question 18

How is a Year data type represented?

Answer 18

YEAR - A year in one of the two formats YY or YYYY

Question 19

What is the format for an ALTER command?

Answer 19

To add a column: ALTER TABLE Employee ADD Department VARCHAR(10)

To delete a column: ALTER TABLE Employee DROP COLUMN HireDate

To change a column data type: ALTER TABLE Employee MODIFY COLUMN EmpName VARCHAR(30) NOT NULL