Slide 7.2: SQL (Structured Query Language)
Slide 7.4: SQL syntax (cont.)
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SQL Syntax

Database Tables
A database most often contains one or more tables. Each table is identified by a name (e.g. Customers or Orders). Tables contain records (rows) with data. Below is an example of a table called Persons:

P_Id LastName FirstName Address City
1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger

The table above contains three records (one for each person) and five columns (P_Id, LastName, FirstName, Address, and City).

SQL Statements
Most of the actions you need to perform on a database are done with SQL statements. The following SQL statement will select all the records in the Persons table: 
 SELECT  LastName  FROM  Persons;
⇒
LastName
Hansen
Svendson
Pettersen
Keep in Mind That...
SQL is not case sensitive.

Semicolon after SQL Statements?
Some database systems require a semicolon at the end of each SQL statement. Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server. The following demonstration may use MySQL database, which does not require to put a semicolon after each SQL statement, but some databases force you to use it.


Demonstration
The following is an SQL test area from W3Schools, which uses the well-known Northwind sample database and the tables are for read only.
For security reasons, the following demonstration may only work in Chrome.

SQL Statement:

Edit the SQL statement and click     to see the result, or    

Result:

Click “Run SQL” to execute the SQL statement above.
W3Schools has created an SQL database in your browser.
The menu to the right displays the database, and will reflect any changes.
Feel free to experiment with any SQL statement.
You can restore the database at any time.
The Database includes:
The Database includes:

TablenamesRecords
Customers91
Categories8
Employees10
OrderDetails518
Orders196
Products77
Shippers3
Suppliers29