Performing math on Decode function tags and moving averages

Question

I have a query shown below to create columns for my report. Can I use the field names as shown in bold to perform math functions? Is there an easy way to do this?
select Data_date,
SUM(DECODE(tag_id,'SEF_F0348I',avg_value,NULL))"TE_Flow_mgd",
SUM(DECODE(tag_id,'L_STEbod_con',avg_value,NULL))"TE_BOD_mgl",
"TE_FLOW_mgd" * "TE_BOD_mgl" * 8.34*.45359 as "KG_BOD"FROM daily_tag_data
Where data_date >= to_date('12/31/2002','mm/dd/yyyy')
GROUP BY data_date;
Also how would I perform a seven day moving average on "KG_BOD"
Thanks - Very new at this.

Answer 1

If you want avoid a sub-query, try this...
select Data_date,
SUM(DECODE(tag_id,'SEF_F0348I',avg_value,NULL))"TE_Flow_mgd",
SUM(DECODE(tag_id,'L_STEbod_con',avg_value,NULL))"TE_BOD_mgl",
SUM(DECODE(tag_id,'SEF_F0348I',avg_value,NULL)) * SUM(DECODE(tag_id,'L_STEbod_con',avg_value,NULL)) * 8.34*.45359 "KG_BOD"
FROM daily_tag_data
Where data_date >= to_date('12/31/2002','mm/dd/yyyy')
GROUP BY data_date;
just replace the 'column-alias' with the actual arithmetic fuction...