Bug in ROW and NULL values with MySQL-4.1 ?

Hi,

I'm wondering if the following is a bug :

How-to-repeat :

SELECT ROW(1,2) IN (ROW(NULL,1));
+---------------------------+
| ROW(1,2) IN (ROW(NULL,1)) |
+---------------------------+
| 0 |
+---------------------------+

SELECT ROW(1,2) IN (ROW(1,NULL));
+---------------------------+
| ROW(1,2) IN (ROW(1,NULL)) |
+---------------------------+
| NULL |
+---------------------------+

SELECT ROW(2,2) IN (ROW(1,NULL));
+---------------------------+
| ROW(2,2) IN (ROW(1,NULL)) |
+---------------------------+
| 0 |
+---------------------------+

If not why in the second case it returns NULL but not for the two other
cases ? :)

Thanks and regards,
Jocelyn


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Re: Bug in ROW and NULL values with MySQL-4.1 ?

Hi!

On Mon, Jan 06, 2003 at 05:55:58PM -0000, Jocelyn Fournier wrote:
> Hi,
>
> I'm wondering if the following is a bug :
>
> How-to-repeat :
>
> SELECT ROW(1,2) IN (ROW(NULL,1));
> +---------------------------+
> | ROW(1,2) IN (ROW(NULL,1)) |
> +---------------------------+
> | 0 |
> +---------------------------+
>
> SELECT ROW(1,2) IN (ROW(1,NULL));
> +---------------------------+
> | ROW(1,2) IN (ROW(1,NULL)) |
> +---------------------------+
> | NULL |
> +---------------------------+
>
> SELECT ROW(2,2) IN (ROW(1,NULL));
> +---------------------------+
> | ROW(2,2) IN (ROW(1,NULL)) |
> +---------------------------+
> | 0 |
> +---------------------------+
>
> If not why in the second case it returns NULL but not for the two other
> cases ? :)

Because it is possible to determinate mismatching without testing NULL
value.

I.e all is clean in first and third cases. but it is unclean in second case,
first value match and second is 'unknown', consequently result is unknown,
too.

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Re: Bug in ROW and NULL values with MySQL-4.1 ?

On Monday 06 January 2003 20:55, Jocelyn Fournier wrote:
> Hi,
>
> I'm wondering if the following is a bug :
>
> How-to-repeat :
>
> SELECT ROW(1,2) IN (ROW(NULL,1));
> +---------------------------+
>
> | ROW(1,2) IN (ROW(NULL,1)) |
>
> +---------------------------+
>
> | 0 |
>
> +---------------------------+
>
> SELECT ROW(1,2) IN (ROW(1,NULL));
> +---------------------------+
>
> | ROW(1,2) IN (ROW(1,NULL)) |
>
> +---------------------------+
>
> | NULL |
>
> +---------------------------+
>
> SELECT ROW(2,2) IN (ROW(1,NULL));
> +---------------------------+
>
> | ROW(2,2) IN (ROW(1,NULL)) |
>
> +---------------------------+
>
> | 0 |
>
> +---------------------------+
>
> If not why in the second case it returns NULL but not for the
> two other cases ? :)


Actually this is not the bug but how the things should work by
definition

A IN (B) is basically the same as A=B

Now as A and B a vectors we have

(a1,a2)=(b2,b2) this is by definition the same as

a1=b1 AND a2=b2

So for the second row it hapens to ne

1=1 AND 2=NULL which is NULL, while for last case it is

2=1 AND 2=NULL which is 0







--
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__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Peter Zaitsev
/ /|_/ / // /\ \/ /_/ / /__ MySQL AB, Full-Time Developer
/_/ /_/\_, /___/\___\_\___/ Moscow, Russia
<___/ www.mysql.com


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