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From:Thimble Smith Date:August 7 1999 9:52pm
Subject:Re: Key Field MUL (Newbie Question)
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At 15:38, 19990807, Anna Winkler wrote:
>When I create a key or index, the value shown in the key field is MUL.
>What does MUL mean?  Is there any way to determine if the field is a key
>or index?

There is no difference between KEY and INDEX - they are synonyms.

MUL means that the key allows multiple rows to have the same value.
That is, it's not a UNIque key.

Tim

>I created a test table with:
>
>mysql> create table key_test (key1 char(10) not null, key2 char(5) not null, index1
> int not null, field4 char(12) not null, primary key (key1), key (key2), index (index1),
> unique (field4));
>Query OK, 0 rows affected (0.01 sec)
>
>So then I have this table:
>
>mysql> describe key_test;
>+--------+----------+------+-----+---------+-------+
>| Field  | Type     | Null | Key | Default | Extra |
>+--------+----------+------+-----+---------+-------+
>| key1   | char(10) |      | PRI |         |       |
>| key2   | char(5)  |      | MUL |         |       |
>| index1 | int(11)  |      | MUL | 0       |       |
>| field4 | char(12) |      | UNI |         |       |
>+--------+----------+------+-----+---------+-------+
>
>I tried a show index:
>
>mysql> show index from key_test;
>+----------+------------+----------+--------------+-------------+-----------+-------------+----------+
>| Table    | Non_unique | Key_name | Seq_in_index | Column_name | Collation |
> Cardinality | Sub_part |
>+----------+------------+----------+--------------+-------------+-----------+-------------+----------+
>| key_test |          0 | PRIMARY  |            1 | key1        | A         |         
>  0 |     NULL |
>| key_test |          1 | key2     |            1 | key2        | A         |       
> NULL |     NULL |
>| key_test |          1 | index1   |            1 | index1      | A         |       
> NULL |     NULL |
>| key_test |          0 | field4   |            1 | field4      | A         |         
>  0 |     NULL |
>+----------+------------+----------+--------------+-------------+-----------+-------------+----------+
>4 rows in set (0.00 sec)
>
>But it still isn't clear to me how I know key2 is a KEY and index1 is an INDEX?
>
>Thanks for your help,
>Anna Winkler
Thread
Key Field MUL (Newbie Question)Anna Winkler7 Aug
  • Re: Key Field MUL (Newbie Question)Thimble Smith7 Aug
  • Re: Key Field MUL (Newbie Question)Sasha Pachev8 Aug
    • Re: Key Field MUL (Newbie Question)Thimble Smith8 Aug