Will this relate the primary keys to one another or just create primary
keys on the columns.
Ie:
Create table test (column1 int(11) not null, column2 int(11) not null,
primary key (column1, column2) )
Then could you...
Insert into test values ("1","2")
Insert into test values ("1","3")
Note that the combination of the two columns represents a distinct value
but column 1 is the same value in both inserts.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Bill Adams
Sent: Monday, November 12, 2001 12:05 PM
To: Brendin
Cc: [EMAIL PROTECTED]
Subject: Re: primary key based on unique value for two columns
Brendin wrote:
> I would like to have a table that has a primary key defined on a
> combination of two columns in the table. In other words a unique key
> based upon the values in two columns.
>
> I don't think I am able to do this in mysql. I think you can only
> have a primary key on one column and not on a combination of columns.
> If I am wrong please correct me.
At least in 3.23.x (x>?) and higher you CAN have a primary key on
multiple columns.
> I am looking for work arounds. I have thought of one. That would be
> to concatenate the columns and use a field terminator such as a - to
> separate the values or (columns) in the single column. Then you could
> use string functions to parse the columns. Ex:
[snip]
There is a maximum key lenth so if you have two char(255) columns you
might need to do something like:
ALTER TABLE table ADD PRIMARY KEY( char_col1(100), char_col2(100));
However, this also means that the combination of the first 100 chars
from each column must be unique.
b.
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