[sqlite] Strange sorting behaviour

[Paolo Vernazza]

I found a strange behaviour when ordering a table where a row is defined 
with  COLLATE NOCASE and the data contains empty strings.

Create a table like this:
CREATE TABLE test (col_a TEXT COLLATE NOCASE, col_b TEXT COLLATE NOCASE);
INSERT INTO test (col_a, col_b) VALUES ('a', '');
INSERT INTO test (col_a, col_b) VALUES ('a', 'a');
INSERT INTO test (col_a, col_b) VALUES ('a', 'b');
INSERT INTO test (col_a, col_b) VALUES ('b', '');
INSERT INTO test (col_a, col_b) VALUES ('b', 'a');
INSERT INTO test (col_a, col_b) VALUES ('b', 'b');
Now select the data using col_b and col_a
SELECT * from test ORDER BY col_b, col_a;
the expected result should be
a|
b|
a|a
b|a
a|b
b|b
but the result is
a|
a|a
b|a
b|
a|b
b|b
To obtain the correct result you must use this query:
SELECT * from test ORDER BY lower(col_b), lower(col_a);
It the table is defined without the "COLLATE NOCASE" definition, the 
sorting works ok with both the queries.

It is a feature or a bug?
I think the problem concerns the empty strings... maybe that when 
COLLATE NOCASE is defined, the comparison between an empty string and 
some data returns EQUAL.

Paolo