Introduction to Select Statements

Question 1

What is a SELECT statement?

Answer 1

A SELECT statement retrieves columns of data from one or more tables or views.

Question 2

What are some ways you can use the SELECT statement?

Answer 2

It can list all columns within a table. It can list specific columns in a table. You can use the SELECT statement to list specific columns and then filter rows with the WHERE statement. You can display columns and list data from multiple tables using a JOIN statement.

Question 3

What order will your columns be displayed in your table?

Answer 3

The order that you list them out in your SELECT statement.

Question 4

If your column has a space in it, like a column that says “First Name,” how would you write it in your SELECT statement?

Answer 4

You would use brackets.

SELECT
VersionDate
, [First Name]

Question 5

How do you display all the columns in a table in your result set?

Answer 5

SELECT *

Question 6

Why is it not good practice to use SELECT *?

Answer 6

Because it decreases performance. It’s better to explicitly define your columns in the SELECT statement.

Question 7

What is a SQL statement?

Answer 7

It is a complete command that performs an action on a database and can include multiple clauses.

Question 7

How do you list the Table Name Syntax in the FROM clause?

Answer 7

server.database.schema.object

Question 7

What does the FROM clause identify?

Answer 7

The table where data will be pulled. If you are pulling from multiple tables, you will identify the relationships in the FROM clause.

Question 7

What is an SQL Clause?

Answer 7

It is a part of a SQL statement that specifies a condition or operation. For example, the FROM clause.

Question 8

What does the WHERE clause do?

Answer 8

It filters the rows of a result set. It can’t filter from tables not listed in the FROM clause. However, it can filter columns not present in the SELECT clause.

Question 8

What does a simple WHERE condition consist of?

Answer 8

It consists of a column, an operator, and a value.

Question 9

When do you need to enclose a value in single quotes in a WHERE clause?

Answer 9

Text and Dates entries need quotes.

Question 10

Which clause type can you compare columns against each other?

Answer 10

In the WHERE clause. WHERE StartDate = EndDate

Question 10

What is the not equal operator in a WHERE statement?

Answer 10

<>

Question 11

What is a Greater Than operator in a WHERE statement?

Answer 11

>

Question 12

What is a Greater Than or Equal Operator in a WHERE statement?

Answer 12

> =

Question 13

What is a Less tHAN or Equal operator in a WHERE statement?

Answer 13

<=

Question 14

What operators string together multiple search conditions?

Answer 14

AND and OR

Question 15

How do you prioritize the order search conditions are executed in the WHERE clause?

Answer 15

Using parenthesis!

Question 16

Which is executed first. The search conditions in the parenthesis or the ones not in the parenthesis in the WHERE clause multiple search condition search statement?

Answer 16

The parenthesis is ordered first!

Question 17

What does the ORDER By Clause do?

Answer 17

It sorts the order of rows in the record set.

Question 18

How do you separate multiple order by clauses?

Answer 18

Using a comma. Example ORDER BY Country, State, LastName

Question 19

How do you sort information in ascending or descending order?

Answer 19

Use ASC and DESC keywords after each column you want sorted.

For example

ORDER BY
Country DESC, State DESC, LastName ASC

Question 20

Why might you use a table alias?

Answer 20

You can use a table alias to tell SQL which which table to refer to if there are columns in multiple tables that have the same name.

Question 21

What’s the order that the SELECT statement is executed in.

Answer 21

FROM
WHERE
SELECT
ORDER BY

Question 22

What clause can you not use alias names? Why is that?

Answer 22

WHERE clause because it is executed before the SELECT clause.

Question 23

What does the DISTINCT keyword do and how do you use it?

Answer 23

DISTINCT eliminates duplicates in a column. You will use it with the SELECT statement. If there are multiple columns in your result set, the entire row must be a duplicate for it to be removed

Question 24

What does SELECT TOP Do?

Answer 24

It limits the number of rows returned.

Question 25

How do you limit the percentage of results?

Answer 25

You can use the PERCENT keyword. Ex. SELECT TOP 10 PERCENT

Question 26

What do you do if you have results that are tied and want to see all the final results with that information?

Answer 26

Use SELECT TOP WITH TIES