Hi Jesper
I was just discussing this with the development manager now and the
following was noted.
- The query was written for mysql 4.0 originally and it seems
that in version 5.0 they had enabled some legacy support stuff ( I am
not too familiar with this as it is before my mysql time ;-) ).
- I have now explained to them what the problem is and they
will be working with the developers to rewrite all these queries.
Regards
Machiel.
On 08/11/2013 13:27, Jesper Wisborg Krogh wrote:
Hi Machiel,
On 8/11/2013 20:04, Machiel Richards wrote:
Good day all
I am hoping someone can assist me in the following.
One of our servers were running mysql 5.0 still and as part
of a phased upgrade route we have upgraded to version 5.1.
However since the upgrade, the query below gives us an error
stating that the syntax is incorrect and I simply cant seem to find
out what is actually wrong as all tests and changes have been giving
us the same.
I have tried many suggestions from the net but to no avail.
The query is as follows:
Using a shorter but equivalent query, you have:
(SELECT t.id, t.name, SUM(val) FROM t1 t)
UNION
(SELECT t.id, t.name, SUM(val) FROM t2 t)
GROUP BY t.id, t.name;
That does not work in 5.0 either (at least in 5.0.96):
ERROR 1064 (42000): You have an error in your SQL syntax; check the
manual that corresponds to your MySQL server version for the right
syntax to use near 'GROUP BY t.id, t.name' at line 4
The issue is that you are trying grouping the entire UNION result, but
at that point there is no SELECT any longer - there is just the result
set. You are also referencing tables that exists inside each of the
SELECT statements, but at the time the GROUP BY is reached, there are
no tables. Note that as written the two SELECT parts will also give
non-deterministic results as you have an aggregate function but no
GROUP BY, so the values of id and val1 will be "random".
What you probably want instead is either:
(SELECT t.id, t.name, SUM(val) FROM t1 t GROUP BY t.id, t.name)
UNION
(SELECT t.id, t.name, SUM(val) FROM t2 t GROUP BY t.id, t.name);
or
SELECT a.id, a.name, SUM(val)
FROM (
(SELECT t.id, t.name, t.val FROM t1 t)
UNION
(SELECT t.id, t.name, t.val FROM t2 t)
) a
GROUP BY a.id, a.name;
On a side note:
AND SUBSTRING(t.Day,1,7) >= '2013-08'
AND SUBSTRING(t.Day,1,7) <= '2013-11')
Assuming t.Day is a date, datetime, or timestamp column, you can
rewrite that WHERE clause to something like (depending on the exact
data type):
t.Day BETWEEN '2013-08-01 00:00:00' AND '2013-11-30 23:59:59'
or
t.Day >= '2013-08-01 00:00:00' AND t.Day < '2013-12-01 00:00:00'
That way you will be able to use an index for that condition.
Best regards,
Jesper Krogh
MySQL Support
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