SQLite

In the query below, there are multiple rows with the same combination of group by columns:
select pgr.productgroupid, r.stationgroupid, sum(quantity)
from tmp_duration d, productgrouprelation pgr, stationgrouprelation r  where d.productid = pgr.productid  and d.stationid = r.stationid group by r.stationgroupid, pgr.productgroupid

results in
Fun EB 13 
Fun EB 12 
Fun EB 1862
GK EB 4 
GK EB 2 
GK EB 505 
GK EB 5 
GK EB 26 
GK EB 6 
GK EB 155 
GK EB 4284 
GK EB 1781 

Reversing the group by columns to "pgr.productgroupid, r.stationgroupid" will give the correct result:
Fun EB 1887 
GK EB 6768 

This effect is also in 3.7.15.2. Version 3.7.2 is ok.

The ORDER BY clause on the final SELECT of the following script does not work:

CREATE TABLE t1(a, b, PRIMARY KEY(a,b));
INSERT INTO t1 VALUES(1,1),(1,2);
CREATE TABLE t2(x, y, PRIMARY KEY(x,y));
INSERT INTO t2 VALUES(3,3),(4,4);
SELECT a, x FROM t1, t2 ORDER BY 1, 2;

This script is a reduction of the same bug that causes the problem in the initial bug report above.

This problem was introduced to trunk by check-in [956e4d7f8958e706] on 2012-10-03 and first appeared in release 3.7.15.

Another test case is shown below. This one uses single-column indices only.

CREATE TABLE t3(a);
INSERT INTO t3 VALUES(1),(1);
CREATE INDEX t3a ON t3(a);
CREATE TABLE t4(x);
INSERT INTO t4 VALUES(3),(4);
CREATE INDEX t4x ON t4(x);
SELECT a, x FROM t3, t4 ORDER BY 1, 2;