At 3:47 PM -0500 05-18-2000, Ruben I Safir wrote:
>Monty
>
>Gooood Morning to You from Brooklyn USA
>
>It seems that the Docs say I can put columns which can be null into an
>index, but it fails to work.
>
>mysql> CREATE TABLE testme (LAST varchar(30), FIRST varchar(30), INDEX
>(LAST, FIRST));
>ERROR 1121: Column 'LAST' is used with UNIQUE or INDEX but is not
>defined as NOT NULL
>mysql>
>
>Are the docs wrong?
You probably don't have MySQL 3.23. That's when NULL values in indexes
were allowed.
>
>KEY is a synonym for INDEX.
> In MySQL, a UNIQUE key can have only distinct values. An error
>occurs if you try to add a new row with a key that matches an existing
> row.
> A PRIMARY KEY is an unique KEY with the extra constraint that all
>key columns must be defined as NOT NULL. In MySQL the key is
> named PRIMARY. A table can have only one PRIMARY KEY. If you don't
>have a PRIMARY KEY and some applications ask for the
> PRIMARY KEY in your tables, MySQL will return the first UNIQUE key,
>which doesn't have any NULL columns, as the PRIMARY KEY.
> A PRIMARY KEY can be a multiple-column index. However, you cannot
>create a multiple-column index using the PRIMARY KEY key
> attibute in a column specification. Doing so will mark only that
>single column as primary. You must use the PRIMARY
> KEY(index_col_name, ...) syntax.
>
>--
>Ruben I Safir
>
>ruben@stripped
>ruben@stripped
>
>Perl Notes:
>http://www.wynn.com/jewish/perl_course
>
>http://www.brooklynonline.com
>Manager of Intranet Development NYU College of Dentistry
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>
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