CODEWITHSUNDEEP
mysqlsqljoin
talom
talom

Reputation: 5

how to Join two different tables and average value between two dates

I have two table, TABLE1 and TABLE2 in the following structure:

TABLE1:

....|VALUE1| STARTDATE|   ENDDATE|....
....|1     |2015-01-01|2015.01.03|.... 
....|2     |2015-01-01|2015.01.04|.... 
....|3     |2015-01-02|2015.01.04|.... 
....|4     |2015-01-03|2015.01.05|....
....|5     |2015-01-03|2015.01.05|....
....|6     |2015-01-03|2015.01.06|....
....|7     |2015-01-04|2015.01.06|....
....|8     |2015-01-04|2015.01.08|....
....|N     |2015-01-04|2015.01.09|....

TABLE2:

          DATE|   TEMPERATURE|....
    2015-01-01|             1|.... 
    2015-01-02|             2|.... 
    2015-01-03|             1|.... 
    2015-01-04|             3|....
    2015-01-05|             2|....
    2015-01-06|             4|....
    2015-01-07|             3|....
    2015-01-08|             3|....
    2015-01-09|             3|....

`

And I'd like to merged them like this:

....|VALUE1| STARTDATE|   ENDDATE| AVG TEMPERATURE|
....|1     |2015-01-01|2015.01.03|             1.3|
....|1     |2015-01-01|2015.01.03|             1.3| 
....|2     |2015-01-01|2015.01.04|            1.75| 
....|3     |2015-01-02|2015.01.04|               2|
....|4     |2015-01-03|2015.01.05|               2|   
....|5     |2015-01-03|2015.01.05|               2|
....|6     |2015-01-03|2015.01.06|             2.5|
....|7     |2015-01-04|2015.01.06|               3|
....|8     |2015-01-04|2015.01.08|               3|
....|N     |2015-01-04|2015.01.09|               3|

so I'd like to calculate the average temperature in this period (between start and end dates) in the new structure.

I tried the following query:

select TABLE1.STARTDATE, TABLE1.ENDDATE,AVG(TABLE2.TEMPERATURE) as AVGTEMPERATURE
from TABLE1
left outer join TABLE2
on TABLE2.Date between TABLE1.STARDATE and TABLE1.ENDDATE

but it doesn't work and shows this message:

Column 'TABLE1.STARDATE' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

Upvotes: 0

Views: 543

Answers (2)

Gordon Linoff
Gordon Linoff

Reputation: 1270633

You need GROUP BY:

select t1.STARTDATE, t1.ENDDATE, AVG(t1.TEMPERATURE) as AVGTEMPERATURE
from TABLE1 t1 left outer join
     TABLE2 t2
     on t2.Date between t1.STARDATE and t1.ENDDATE
group by t1.STARTDATE, t1.ENDDATE;

Upvotes: 1

Zaynul Abadin Tuhin
Zaynul Abadin Tuhin

Reputation: 31991

try like below by using subquery

   select b.*,a.* from from TABLE1 b
   left outer join 
   ( select t2.*,t1.avgtemp  from
    ( select VALUE1, avg(TEMPERATURE) as avgtemp from
    TABLE2 group by VALUE1 
    ) t1 join TABLE2 t2 on t1.VALUE1=t2.VALUE1
    ) a on on a.Date between b.STARDATE and b.ENDDATE

you got the error because you used aggregate function avg and select all the columns of table but nothing used in group by

Upvotes: 0

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