mysql union all with aliases, syntax error - mysql

Question

Why do I get
Error in query (1064): Syntax error near 'as q2)' at line 7
with
SELECT SQL_NO_CACHE q1.d1, q1.a, q2.b, (q1.a-q2.b)/q1.a*100 as Percentage
FROM
(SELECT Date(date) d1, count(id_update) a
FROM vas_updates
WHERE date > date_sub(now(), interval 2 hour)
GROUP BY DATE(date)) as q1
UNION ALL
(SELECT date(date) as d2, count(id_update) as b
FROM vas_updates
WHERE date BETWEEN
date_sub(date_sub(now(), interval 1 day), interval 2 hour)
AND
date_sub(now(), interval 1 day) group by DATE(d2) ) as q2
Can't I use aliases with UNION?
UPDATE:
this query might have leftovers from another query, I was tyring to understand the syntax error first.
What I'm trying to calculate is the percentage increase or decrease of two sums which are the hits from the last 2 hours of today compared to same timeframe from yesterday.
the table has just id and datetime

Answer 1

I suspect you actually want a JOIN
Something like this:-
SELECT SQL_NO_CACHE q1.d1, q1.a, q2.b, (q1.a-q2.b)/q1.a*100 as Percentage
FROM
(
SELECT Date(date) d1, count(id_update) a
FROM vas_updates
WHERE date > date_sub(now(), interval 2 hour)
GROUP BY DATE(date)
) as q1
INNER JOIN
(
SELECT date(date) as d2, count(id_update) as b
FROM vas_updates
WHERE date BETWEEN date_sub(date_sub(now(), interval 1 day), interval 2 hour) AND date_sub(now(), interval 1 day)
group by DATE(d2)
) as q2
ON q1.d1 = q2.d2
EDIT
Checked your updated query and it IS a JOIN you need.
You can use a CROSS JOIN. You are returning 1 value from each sub query, and doing a calculation on those values:-
SELECT SQL_NO_CACHE q1.d1, q1.a, q2.b, (q1.a-q2.b)/q1.a*100 as Percentage
FROM
(
SELECT MIN(Date(date)) d1, count(id_update) a
FROM vas_updates
WHERE date > date_sub(now(), interval 2 hour)
) as q1
CROSS JOIN
(
SELECT MIN(Date(date)) d2, count(id_update) as b
FROM vas_updates
WHERE date BETWEEN
date_sub(date_sub(now(), interval 1 day), interval 2 hour)
AND
date_sub(now(), interval 1 day)
) as q2
CROSS JOIN gives you every combination of the rows. In this case you have 1 resulting record. I have just returned the MIN date to get a single date to display.

Answer 2

You Can't. A UNION operation does not allow you to use alias on subqueries as it is an operation that creates a single table.
Like this:
select 1 a, 2 b
union all
select 3 blah, 4 bleh
This will result in
a b
1 2
3 4
See it here: http://sqlfiddle.com/#!2/68b32/444
On this query you only have two fields no matters what is on the second query it will only parse the first one, check if the others querys has the same quantity of fields as the first and if they are of the same type. Name the UNIONed querys with alies is invalid.
So I think what you need is probably a JOIN OR just all the fields
So, your query would be something like:
SELECT SQL_NO_CACHE tbl.d1,
tbl.a,
tbl.b,
(tbl.a-tbl.b)/tbl.a*100 as Percentage
FROM (SELECT Date(date) d1,
count(id_update) a,
null d2,
null b
FROM vas_updates
WHERE date > date_sub(now(), interval 2 hour)
GROUP BY DATE(date)
UNION ALL
SELECT null d1,
null a
date(date) as d2,
count(id_update) as b
FROM vas_updates
WHERE date
BETWEEN date_sub(date_sub(now(), interval 1 day), interval 2 hour)
AND date_sub(now(), interval 1 day) group by DATE(d2)
) tbl
But this most likely will not make the calculations right. You can use the version that #Kickstart has provided you.
Query of the answer from #Kickstart
SELECT SQL_NO_CACHE q1.d1, q1.a, q2.b, (q1.a-q2.b)/q1.a*100 as Percentage
FROM
(
SELECT Date(date) d1, count(id_update) a
FROM vas_updates
WHERE date > date_sub(now(), interval 2 hour)
GROUP BY DATE(date)
) as q1
INNER JOIN
(
SELECT date(date) as d2, count(id_update) as b
FROM vas_updates
WHERE date BETWEEN date_sub(date_sub(now(), interval 1 day), interval 2 hour) AND date_sub(now(), interval 1 day)
group by DATE(d2)
) as q2
ON q1.d1 = q2.d2
I decided to put this answer to explain why you are using the UNION operation in a wrong way.

Answer 3

I think that #Kickstart is right,and you can try this.
SELECT SQL_NO_CACHE d, a
FROM
(SELECT Date(date) d, count(id_update) as a
FROM vas_updates
WHERE date > date_senter code hereub(now(), interval 2 hour)
GROUP BY DATE(date))
UNION ALL
(SELECT date(date) as d, count(id_update) as a
FROM vas_updates
WHERE date BETWEEN
date_sub(date_sub(now(), interval 1 day), interval 2 hour)
AND
date_sub(now(), interval 1 day) group by DATE(d2) )
I'm wrong,UPDATE, you can try like this
SELECT SQL_NO_CACHE q1.d1, q1.a, q2.b, (q1.a-q2.b)/q1.a*100 as Percentage
FROM
(
SELECT DATE_FORMAT(Date(date),'%H') as d1, count(id_update) a
FROM vas_updates
WHERE date > date_sub(now(), interval 2 hour)
GROUP BY DATE(date)
) as q1
INNER JOIN
(
SELECT DATE_FORMAT(Date(date),'%H') as d2, count(id_update) as b
FROM vas_updates
WHERE date BETWEEN date_sub(date_sub(now(), interval 1 day), interval 2 hour) AND date_sub(now(), interval 1 day)
group by DATE(d2)
) as q2
ON q1.d1 = q2.d2