Primary Key - A problem understanind its Function!

[npsari]

I created a database...

 

Now, I am about to create a table

 

It says I have to create a Primary key for the Table!

 

I dont understand what is the point of this primary key

 

The user has 3 fields to fill-in  in my Form

Name:

Occupation:

Age:

 

So, Do i have to create a new field (in the HTML Form) which asks the user to insert a unique ID (As this unique key)

 

Can someone please explain how this ID key works

[hellouthere]

unique keys help with organisation... add a field at the beginning of your table... set it to "Auto Increment" and as the primary key... this is a good practise when making database tables...

[npsari]

Thanks for your reply

 

However, I already know that

 

You didnt answer my question

[Barand]

Each record must have a unique identifier (or the dbms does not know which one you want to update or delete)  but it doesn't have to be an ID field. For example, if it's person then you could use their National Insurance Number/Social Security number as the PK since it is unique and you are storing it already. Or, for an invoice table, use the invoice number.

 

In your table none of the fields would be unique (name, occupation, age) as any could reasonably be duplicated. Therefore the easiest way in that case is to create an auto-incrementing id as the PK

[npsari]

So who gives the value of this Key

Does it happen automatically?

 

or does the user Fill it in?

 

What if I called the key ID, therefore, the table has 4 rows

 

ID:

Name:

Accupation:

Age:

 

And the user only submitted the last 3 (Name, occupation, ID) in the HTML form

 

What happens?

[Barand]

if you define your table with, say,

CREATE TABLE mytablename (
  ID int not null auto_increment primary key,
  name varchar (50),
  occupation varchar (50),
  age tinyint
)

 

The the user need not be aware that the key exist. They enter name, occupation and age and you insert those values

 

INSERT INTO mytablename (name, occupation, age) VALUES ('$name', '$occupation', '$age')

 

Note there is no mention of the id field. Mysql takes care of it for you, generating the next value as each row is added.

[idevlabsdotcom]

just let the database handle assigning a unique key by setting the field option to auto_increment.  there's no reason for you to mess with the key yourself in this particular situation.