maria-developers team mailing list archive

[Alexander Barkov <bar@xxxxxxxxxxx>]

Hi,


On 05/04/2016 12:52 AM, Alexander Barkov wrote:
> Hi Sergei,
>
>
> If I run this query:
>
> SELECT 1 UNION SELECT 2 INTO OUTFILE 'test.txt';
>
> It creates a file 'test.txt' with this content:
>
> 1
> 2
>
> Looks fine so far.
>
>
> Now if I do "rm test.txt" and execute another query (with parentheses):
>
> (SELECT 1) UNION (SELECT 2 INTO OUTFILE 'test.txt');
>
> it still puts the same two records from both UNION parts!
> This looks confusing, as parentheses a kind of assume that only
> the right UNION part is to be exported.

INTO @v1 is also confusing and is applied to the entire UNION,
rather than a UNION part:


(SELECT 1) UNION ALL (SELECT * FROM t1 LIMIT 1 INTO @v1);
ERROR 1172 (42000): Result consisted of more than one row



> Exporting only one UNION part is not supported, IIRC.
> So the above query should probably return a syntax error.
>
>
> But now there is a new trouble. There is no syntax like this:
>
> (SELECT ...) UNION (SELECT ...) INTO OUTFILE 'test.txt';
>
>
>
> So instead of:
>
> (SELECT ...) UNION (SELECT ... INTO OUTFILE 'test.txt');
>
> one will have to write this:
>
> SELECT * INTO OUTFILE 'test.txt'
> FROM ((SELECT ...) UNION (SELECT ...)) AS t1;
>
> The latter looks longer, but at least it's not confusing as the former.