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Alan @ CIT · 02-09-2008, 07:23 PM

I'm not sure what you mean by shared columns.

The idea behind using joins is to split data across multiple tables. For example, say you have a users table:

Code:

userid | username | password
----------------------------
1      | alan     | secret
2      | orc      | something

And you decide to store the users email addresses in a seperate 'emails' table:

Code:

emailid | address | userid
--------------------------
...more rows here...
15       | alan@example.com | 1
16       | orc@example.com  | 2

You can see that the 'userid' column in our 'users' table, matches the 'userid' column in our 'emails' table. If we wanted to fetch a username and their email address, we would do a join across the two tables using the 'userid' column to get the data we wanted.

Is this what you meant by shared columns?

Alan

02-09-2008, 07:23 PM	#4 (permalink)
Alan @ CIT Member of the Month The Frequenter Join Date: Apr 2005 Location: South UK Posts: 483 Thanks: 51	I'm not sure what you mean by shared columns. The idea behind using joins is to split data across multiple tables. For example, say you have a users table: Code: userid \| username \| password ---------------------------- 1 \| alan \| secret 2 \| orc \| something And you decide to store the users email addresses in a seperate 'emails' table: Code: emailid \| address \| userid -------------------------- ...more rows here... 15 \| alan@example.com \| 1 16 \| orc@example.com \| 2 You can see that the 'userid' column in our 'users' table, matches the 'userid' column in our 'emails' table. If we wanted to fetch a username and their email address, we would do a join across the two tables using the 'userid' column to get the data we wanted. Is this what you meant by shared columns? Alan