Isn't this as simple as something like:

select a.id, a.order_number, a.material, a.date_time,
sum(t.tempo_o1)/6 as temp_o1_av,
sum(t.tempo_o2)/6 as temp_o2_av,
sum(t.tempo_o3)/6 as temp_o3_av
from activities a
join temperatures t on a.id = t.activity_id
group by 1, 2, 3, 4

HTH,
Set

William Gonzáles Sánchez wrote:

> Hello everybody. I have 2 tables:
>
> 1)
> ACTIVITIES
>
> ID ORDER_NUMBER MATERIAL DATE_TIME
> ------------------------------------------------------------------------------
> 100 OF200709FR-0556 3240HD-48 14.09.2007 15:53:53
> 101 OF200709FR-0556 511 14.09.2007 16:00:55
>
>
> 2)
> TEMPERATURES
>
> ID ACTIVITY_ID TEMPO_01 TEMPO_02 TEMPO_03
> 1000 100 144 153
> 100
> 1001 100 146 151
> 101
> 1002 100 151 150
> 110
> 1003 100 162 148
> 106
> 1004 100 159 145
> 110
> 1005 100 163 146
> 107
> 1007 101 144 153
> 120
> 1008 101 146 151
> 115
> 1009 101 151 150
> 125
> 1010 101 162 148
> 123
> 1011 101 163 147
> 135
> 1012 101 159 145
> 103
>
>
> In ACTIVITIES table, I have the main rows. Each row in ACTIVITIES, has 6
> "child" rows in TEMPERATURES. I need a sql query that gives me these
> results:
>
> ACTIVITIES.ID ORDER_NUMBER MATERIAL DATE_TIME
> TEMP_01_AV TEMP_02_AV TEMP_03_AV
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> 100 OF200709FR-0556 3240HD-48
> 14.09.200715:53:53 120 130
> 110
> 101 OF200709FR-0556 511
> 14.09.2007 16:00:55 115 125
> 104
>
>
> As you can see, I need all fields from table ACTIVITIES and the 6 values
> average from table TEMPERATURES (TEMP_01_AV, TEMP_02_AV,TEMP_03_AV) for each
> activity.
>
> Please, help me to do the SQL query.
>
> Thanks in advance.
> William GS