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Re: UNION + INTO OUTFILE is confusing
On 05/04/2016 12:52 AM, Alexander Barkov wrote:
If I run this query:
SELECT 1 UNION SELECT 2 INTO OUTFILE 'test.txt';
It creates a file 'test.txt' with this content:
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.