How can I calculate a dot product in SQL - sql

Question

This is similar to this post, but different enough that I'm asking again. The proposed solutions would also be impractically slow in my case.
Note: I am also working with really large datasets in Redshift.
I am trying to calculate "scores" for a statistical model, which requires that I calculate a dot product for every row in a data set. In particular, I would like to create a new column in my table "SCORE" that multiplies the values for each column in the first table by a pre-specified value for that column.
For example, I have the following tables:
INITIAL
+--------+------+-------+
| NAME | COL0 | COL1 |
+--------+------+-------+
| AL | 1 | 4 |
| BILL | 2 | 5 |
| CATHY | 3 | 6 |
+--------+------+-------+
ESTIMATES
+--------+----------+
| NAME | ESTIMATE |
+--------+----------+
| COL0 | 5 |
| COL1 | 10 |
+--------+----------+
and I want a final table,
FINAL
+--------+------+-------+-------+
| NAME | COL0 | COL1 | SCORE |
+--------+------+-------+-------+
| AL | 1 | 4 | 45 |
| BILL | 2 | 5 | 60 |
| CATHY | 3 | 6 | 75 |
+--------+------+-------+-------+
For the final table, the values for each column in the INITIAL table is multiplied by a different number depending on the values listed in the ESTIMATES table
For example, the SCORE for AL is derived from 1 * 5 + 4 * 10 = 45. Where the 5 and 10 come from the estimates table.
Currently, I am creating the SCORE column by writing SQL code that manually writes in the numbers from the estimates.

Answer 1

You can do this by joining the tables and then using conditional aggregation:
select i.name,
max(i.col0) * max(case when e.name = 'col0' then estimate end) as col0,
max(i.col1) * max(case when e.name = 'col1' then estimate end) as col1,
(max(i.col0) * max(case when e.name = 'col0' then estimate end) +
max(i.col1) * max(case when e.name = 'col1' then estimate end)
) as score
from initial i cross join
estimates e
group by i.name;

Answer 2

Assuming estimates table will always result in one row when pivoting using case...
SELECT i.name, i.col0, i.col1, (pest.mcol0*i.col0+pest.mcol1*i.col1) as score
FROM Initial
CROSS JOIN
(select
max(case name when 'COL0' then estimate end) as mcol0,
max(case name when 'Col1' then estimate end) as mcol1
FROM estimates) Pest -- pivot Estimate

Answer 3

You can do that by joining the tables as:
SELECT i.NAME,i.COL0,i.COL1,
(MAX(i.COL0) * MAX(CASE WHEN e.name = 'COL0' THEN estimate end) +
MAX(i.COL1) * MAX(CASE WHEN e.name = 'COL1' THEN estimate end)) AS SCORE
FROM INITIAL i CROSS JOIN ESTIMATES E GROUP BY i.NAME,i.COL0,i.COL1 ORDER BY NAME;
Please refer this SQLFiddle Link as reference

Answer 4

For future-comers, a postgresql implementation of vector dot product is available here:
CREATE OR REPLACE FUNCTION public.dot_product(IN vector1 double precision[], IN vector2 double precision[])
RETURNS double precision
AS $BODY$
BEGIN
RETURN(SELECT sum(mul) FROM (SELECT v1e*v2e as mul FROM unnest(vector1, vector2) AS t(v1e,v2e)) AS denominator);
END;
$BODY$ LANGUAGE 'plpgsql';