At 3:35 +0800 6/14/02, Andy Sy wrote:
>----- Original Message -----
>From: "Paul DuBois" <paul@stripped>
>To: "Andy Sy" <andy@stripped>; <mysql@stripped>
>Sent: Friday, June 14, 2002 2:45 AM
>Subject: Re: Why does Key==Mul in DESCRIBE TABLE for unique key?
>
>
>> At 2:03 +0800 6/14/02, Andy Sy wrote:
>> >mysql> CREATE TABLE X (FLD1 INT UNIQUE);
>> >Query OK, 0 rows affected (0.05 sec)
>> >
>> >mysql> DESCRIBE X;
>> >+-------+---------+------+-----+---------+-------+
>> >| Field | Type | Null | Key | Default | Extra |
>> >+-------+---------+------+-----+---------+-------+
>> >| FLD1 | int(11) | YES | MUL | NULL | |
>> >+-------+---------+------+-----+---------+-------+
>> >
>> >Doesn't MUL mean a key can exist multiple times
>> >in the index?
>>
>> Right. It means it's part of a non-unique index.
>
>But I declared the field as UNIQUE (see the CREATE
>TABLE statement).
UNIQUE indexes can contain multiple NULL values.
Declare the column as FLD1 INT NOT NULL UNIQUE
and you'll see a difference.
