SQL Matrix Manipulations Two random 3x3 (N = 3) matrices have been provided in t

Question

SQL Matrix Manipulations

Two random 3x3 (N = 3) matrices have been provided in tables A and B, having the following schema:

i INT: Row index

j INT: Column index

val INT: Cell value

We want the elementwise multiply of matrices A and B. That is, (A·B)ij = AijBij for all i, j. Write a single SQL query that performs this operation (in the same format as Aoutput tuples should be of format (i, j, val) where i is row, j is column, and the output is ordered by row then column index).

For example:

select*from A;
0|0|7
0|1|5
0|2|8
1|0|10
1|1|7
1|2|7
2|0|2
2|1|0
2|2|5

select* from B;
0|0|9
0|1|6
0|2|10
1|0|7
1|1|6
1|2|9
2|0|1
2|1|1
2|2|7

should result :

i j val

0 0 63

0 1 30

0 2 80

1 0 70

1 1 42

1 2 63

2 0 2

2 1 0

2 2 35

Explanation / Answer

CREATE TABLE a ( row_num INT, col_num INT, value INT, PRIMARY KEY(row_num, col_num) ); CREATE TABLE b ( row_num INT, col_num INT, value INT, PRIMARY KEY(row_num, col_num) );

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