I have a table svn1:
id | date | startdate
23 2002-12-04 2000-11-11
23 2004-08-19 2005-09-10
23 2002-09-09 2004-08-23
select id,startdate from svn1 where startdate>=(select max(date) from svn1 where id=svn1.id);
Now the problem is how do I let know the subquery to match id with the id in the outer query. Obviously id=svn1.id wont work. Thanks!
If you have the time to read more:
This really is a simplified version of asking what I really am trying to do here. my actual query is something like this
select
id, count(distinct archdetails.compname)
from
svn1,svn3,archdetails
where
svn1.name='ant'
and svn3.name='ant'
and archdetails.name='ant'
and type='Bug'
and svn1.revno=svn3.revno
and svn3.compname=archdetails.compname
and
(
(startdate>=sdate and startdate<=edate)
or
(
sdate<=(select max(date) from svn1 where type='Bug' and id=svn1.id)
and
edate>=(select max(date) from svn1 where type='Bug' and id=svn1.id)
)
or
(
sdate>=startdate
and
edate<=(select max(date) from svn1 where type='Bug' and id=svn1.id)
)
)
group by id LIMIT 0,40;
As you notice select max(date) from svn1 where type='Bug' and id=svn1.id
has to be calculated many times.
Can I just calculate this once and store it using AS
and then use that variable later. Main problem is to correct id=svn1.id
so as to correctly equate it to the id in the outer table.
I'm not sure you can eliminate the repetition of the subquery, but the subquery can reference the main query if you use a table alias, as in the following:
select id,
count(distinct archdetails.compname)
from svn1 s1,
svn3 s3,
archdetails a
where s1.name='ant' and
s3.name='ant' and
a.name='ant' and
type='Bug' and
s1.revno=s3.revno and
s3.compname = a.compname and
( (startdate >= sdate and startdate<=edate) or
(sdate <= (select max(date)
from svn1
where type='Bug' and
id=s1.id and
edate>=(select max(date)
from svn1
where type='Bug' and
id=s1.id)) or
(sdate >= startdate and edate<=(select max(date)
from svn1
where type='Bug' and
id=s1.id)) )
group by id LIMIT 0,40;
Share and enjoy.
尝试使用别名,这样的东西应该工作:
select s.id,s.startdate from svn1.s where s.startdate>=(select max(date) from svn1.s2 where s.id=s2.id);
You should be able to left join to a sub-select so you only run the query once. Then you can do a join condition to pull out the maximum for the ID on each record as shown below:
SELECT id,
COUNT(DISTINCT archdetails.compname)
FROM svn1,
svn3,
archdetails
LEFT JOIN (
SELECT id, MAX(date) AS MaximumDate
FROM svn1
WHERE TYPE = 'Bug'
GROUP BY id
) AS MaxDate ON MaxDate.id = svn1.id
WHERE svn1.name = 'ant'
AND svn3.name = 'ant'
AND archdetails.name = 'ant'
AND TYPE = 'Bug'
AND svn1.revno = svn3.revno
AND svn3.compname = archdetails.compname
AND (
(startdate >= sdate AND startdate <= edate)
OR (
sdate <= MaxDate.MaximumDate
AND edate >= MaxDate.MaximumDate
)
OR (
sdate >= startdate
AND edate <= MaxDate.MaximumDate
)
)
GROUP BY
id LIMIT 0,
40;
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