SQL PART 4C

Original Table (used in the examples)

LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Svendson Tove Borgvn 23 Sandnes
Svendson Stephen Kaivn 18 Sandnes
Example

Use AND to display each person with the first name equal to "Tove", and the last name equal to "Svendson":

SELECT * FROM Persons WHERE FirstName='Tove' AND LastName='Svendson'

Result:

LastName FirstName Address City
Svendson Tove Borgvn 23 Sandnes

Example

Use OR to display each person with the first name equal to "Tove", or the last name equal to "Svendson":

SELECT * FROM Persons WHERE firstname='Tove' OR lastname='Svendson'

Result:
LastName FirstName Address City
Svendson Tove Borgvn 23 Sandnes
Svendson Stephen Kaivn 18 Sandnes
Example

You can also combine AND and OR (use parentheses to form complex expressions):

SELECT * FROM Persons WHERE

(FirstName='Tove' OR FirstName='Stephen')

AND LastName='Svendson'

Result:

LastName FirstName Address City

Svendson Tove Borgvn 23 Sandnes
Svendson Stephen Kaivn 18 Sandnes

SQL IN

The IN operator may be used if you know the exact value you want to return for at least one of the columns.

SELECT column_name FROM table_name WHERE column_name IN (value1,value2,..)

Original Table (used in the examples)

LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Nordmann Anna Neset 18 Sandnes
Pettersen Kari Storgt 20 Stavanger
Svendson Tove Borgvn 23 Sandnes

Example 1

To display the persons with LastName equal to "Hansen" or "Pettersen", use the following SQL:

SELECT * FROM Persons WHERE LastName IN ('Hansen','Pettersen')
Result:
LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Pettersen Kari Storgt 20 Stavanger

SQL BETWEEN

BETWEEN ... AND

The BETWEEN ... AND operator selects a range of data between two values. These values can be numbers, text, or dates.

SELECT column_name FROM table_name WHERE column_name  BETWEEN value1 AND value2

Original Table (used in the examples)

LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Nordmann Anna Neset 18 Sandnes
Pettersen Kari Storgt 20 Stavanger
Svendson Tove Borgvn 23 Sandnes

Example 1

To display the persons alphabetically between (and including) "Hansen" and exclusive "Pettersen", use the following SQL:

SELECT * FROM Persons WHERE LastName  BETWEEN 'Hansen' AND 'Pettersen'

Result:
LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Nordmann Anna Neset 18 Sandnes

IMPORTANT! The BETWEEN...AND operator is treated differently in different databases. With some databases a person with the LastName of "Hansen" or "Pettersen" will not be listed (BETWEEN..AND only selects fields that are between and excluding the test values). With some databases a person with the last name of "Hansen" or "Pettersen" will be listed (BETWEEN..AND selects fields that are between and including the test values). With other databases a person with the last name of "Hansen" will be listed, but "Pettersen" will not be listed (BETWEEN..AND selects fields between the test values, including the first test value and excluding the last test value). Therefore: Check how your database treats the BETWEEN....AND operator!

Example 2

To display the persons outside the range used in the previous example, use the NOT operator:

SELECT * FROM Persons WHERE LastName  NOT BETWEEN 'Hansen' AND 'Pettersen'

Result:

LastName FirstName Address City
Pettersen Kari Storgt 20 Stavanger
Svendson Tove Borgvn 23 Sandnes

SQL Aliases

With SQL, aliases can be used for column names and table names.

Column Name Alias
The syntax is:
SELECT column AS column_alias FROM table

Table Name Alias

The syntax is:

SELECT column FROM table AS table_alias

Example: Using a Column Alias
This table (Persons):
LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Svendson Tove Borgvn 23 Sandnes
Pettersen Kari Storgt 20 Stavanger

And this SQL:

SELECT LastName AS Family, FirstName AS Name FROM Persons

Returns this result:
Family Name
Hansen Ola
Svendson Tove
Pettersen Kari

Example: Using a Table Alias

This table (Persons):
LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Svendson Tove Borgvn 23 Sandnes
Pettersen Kari Storgt 20 Stavanger

And this SQL:
SELECT LastName, FirstName FROM Persons AS Employees

Returns this result:
Table Employees:
LastName FirstName
Hansen Ola
Svendson Tove
Pettersen Kari

SQL Join

Joins and Keys

Sometimes we have to select data from two or more tables to make our result complete. We have to Perform a join.
Tables in a database can be related to each other with keys. A primary key is a column with a unique value for each row. The purpose is to bind data together, across tables, without repeating all of the data in every table.

In the "Employees" table below, the "Employee_ID" column is the primary key, meaning that no two rows can have the same Employee_ID. The Employee_ID distinguishes two persons even if they have the same name.

When you look at the example tables below, notice that:
The "Employee_ID" column is the primary key of the "Employees" table

The "Prod_ID" column is the primary key of the "Orders" table

The "Employee_ID" column in the "Orders" table is used to refer to the persons in the "Employees" table without using their names

Employees:

Employee_ID Name

01 Hansen, Ola

02 Svendson, Tove

03 Svendson, Stephen

04 Pettersen, Kari