Data commit

Task/Matrix-multiplication/SQL/matrix-multiplication.sql

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+CREATE TABLE a (x integer, y integer, e real);
+CREATE TABLE b (x integer, y integer, e real);
+
+-- test data
+-- A is a 2x2 matrix
+INSERT INTO a VALUES(0,0,1); INSERT INTO a VALUES(1,0,2);
+INSERT INTO a VALUES(0,1,3); INSERT INTO a VALUES(1,1,4);
+
+-- B is a 2x3 matrix
+INSERT INTO b VALUES(0,0,-3); INSERT INTO b VALUES(1,0,-8); INSERT INTO b VALUES(2,0,3);
+INSERT INTO b VALUES(0,1,-2); INSERT INTO b VALUES(1,1, 1); INSERT INTO b VALUES(2,1,4);
+
+-- C is 2x2 * 2x3 so will be a 2x3 matrix
+SELECT rhs.x, lhs.y, (SELECT sum(a.e*b.e) FROM a, b
+                             WHERE a.y = lhs.y
+                               AND b.x = rhs.x
+                               AND a.x = b.y)
+       INTO TABLE c
+       FROM a AS lhs, b AS rhs
+       WHERE lhs.x = 0 AND rhs.y = 0;