Querying in SQL

Question 1

What is the SELECT statement, and what statement is it used with?

Answer 1

Basic statement that is used to retrieve data from a SQL database; used with the FROM statement.

Question 2

Clause that is used to filter certain results being returned

Answer 2

WHERE

Question 3

What are standard numerical operators (6)?

Clause: ???

Answer 3

=, !=, , >=

I.E.
Col_name != 4

Clause: WHERE

Question 4

Number is within range of two values (inclusive)

Clause: ???

Answer 4

BETWEEN … AND …

I.E.
Col_name BETWEEN 1.5 AND 5

Clause: WHERE

Question 5

Number is not within range of two values (inclusive)

Clause: ????

Answer 5

NOT BETWEEN … AND …

I.E.
Col_name NOT BETWEEN 3 AND 5

Clause: WHERE

Question 6

Number exists in a list
String exists in a list
Clause: ????

Answer 6

IN (…)

I.E.
Col_name IN (2, 4, 6)
Col_name IN ("A", "B", "C")

Clause: WHERE

Question 7

Number does not exist in a list
String does not exist in a list
Clause: ????

Answer 7

NOT IN (…)

I.E.
Col_name NOT IN (1, 2, 3)
Col_name NOT IN (“A”, “B”, “C”)

Clause: WHERE

Question 8

Case sensitive exact string comparison

Answer 8

=

I.E.
Col_name = “abc”

Question 9

Case sensitive exact string inequality comparison

Answer 9

!=,

I.E.
Col_name != “xyza”

Question 10

Case INSENSITIVE exact string comparison

Answer 10

LIKE

I.E.
Col_name LIKE “fgh”

Question 11

Case INSENSITIVE exact string inequality comparison

Answer 11

NOT LIKE

I.E.
Col_name NOT LIKE “gnhc”

Question 12

Used anywhere in a string to match a sequence of zero or more characters

Used with something.

Answer 12

%

I.E.
Col_name LIKE “%AT%” (matches “AT”, “ATTIC”, “CAT” or even “BRATS”)

used with LIKE and NOT LIKE

Question 13

Used anywhere in a string to match a single character

Used with something

Answer 13

_

I.E.
Col_name LIKE “AN_” (matches “AND”, but not “AN”)

used with LIKE and NOT LIKE

Question 14

What is the DISTINCT clause?

With what statement is it used?

Answer 14

Discard rows that have a duplicate column value; SELECT statement.

Question 15

What is the purpose of the ORDER BY clause?

And what is commonly used with it?

Answer 15

The ORDER BY clause is a way to sort results by a given column in ascending or descending order.

The LIMIT will reduce the number of rows to return, and OFFSET will specify where to begin counting the number rows from.

Question 16

What is the purpose of the INNER JOIN clause?

Answer 16

Process that matches rows from the first table and the second table which have the same key to create a result row with the combined columns from both tables.

Question 17

What is a LEFT JOIN?
RIGHT JOIN?
FULL JOIN?

Answer 17

When joining table A to table B, a LEFT JOIN simply includes rows from A regardless of whether a matching row is found in B.

RIGHT JOIN is same as LEFT JOIN but reversed; keeping rows in B regardless of whether a matching row was found in A.

FULL JOIN means that rows from both tables are kept, regardless of whether a there is a matching row in the other table.

Question 18

Clause that IS NULL/IS NOT NULL is used with.

Answer 18

WHERE