Spreadsheet programs (such as Microsoft Excel) have row numbers to identify what row a certain bit of data is in.
Databases have a similar identifier, called the Primary Key.
You can draw out your database with relative ease - or you can create a mock up of it in a spreadsheet.
For example:
This is a graphical representation of our code example on the previous page. Seems easy when you look at it, right?
How do I remember what the primary key is when I make a new row of data?
When you create the tables, there are going to be more options that you need to include to make your database a little easier to use...specifically being AUTO_INCREMENT and NULL / NOT NULL.
First, the code example...
<?php
// Make a MySQL Connection
mysql_connect("localhost", "user", "password") or die(mysql_error());
mysql_select_db("test_db") or die(mysql_error());
// Create a MySQL table in the selected database
mysql_query("CREATE TABLE Employees(
id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id),
employee_id INT,
first_name VARCHAR(50),
last_name VARCHAR(50)")
or die(mysql_error());
echo "Table Created!";
?>
Let’s run through this one, step by step.
First, we make a connection to the MySQL database and select the database we want to work on.
Then, we make a table called “Employees”, with a column called “id” that will automatically increment by 1 each time a new record is created, has a NOT NULL value (this simply means that the “id” value is real and searchable), and that the Primary Key is set to be the “id” field.
Now, we create our three data fields (employee_id, first_name, last_name), and issue the good ol’ “or die” command to tell us if something went wrong.