1. What is the simplest SQL retrieval?
The simplest versions of the most important SQL command are SELECT, FROM statement. Then if you need to limit the result you introduce the WHERE clause. In the WHERE clause you can use operators such as LIKE, AND, OR, EQUAL, BETWEEN and IN.

2. What is the purpose of the Where clause when using SELECT?
The purpose of this clause is to be able to list any conditions that are to be applied to the data retrieved.

3. What are data types and why are they important?

A data type is a classification identifying one of various types of data, they are important because

assigning data types gives meaning to collections of information

4. Provide an example of the GROUP by clause, when would you use this clause?

SELECT Salesperson, SUM(Revenue) AS ‘Total’, MIN(Revenue) AS ‘Smallest’, MAX(Revenue) AS ‘Largest’, AVG(Revenue) AS ‘Average’, COUNT(Revenue) AS ‘Number’

FROM Orders

GROUP BY Salesperson

You use this clause when you need to see the information in a certain order

5. What is an aggregate function (provide 4)? How are they used?

An aggregate function is a function where the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning or measurement

AVG() - Returns the average value (average)

COUNT() - Returns the number of rows (count)

FIRST() - Returns the first value

LAST() - Returns the last value

6. Provide example using the COUNT() function

SELECT COUNT(*)

FROM employees

WHERE salary > 25000;

7. How is a field name qualified? How is this used when using a JOIN command, why is it important?

A Field name is qualified by preceding the name of the filed with the name by the table followed by a period. This is used when using the JOIN command when there is potential doubt in listing the field names. This is