a	b
1	2
2	3
3	5
4	5
5	5
6	6
7	7
8	9
FOUND_ROWS()
8
a	b
1	2
FOUND_ROWS()
8
a	b
8	9
FOUND_ROWS()
8
b
2
FOUND_ROWS()
6
b	c
5	3
FOUND_ROWS()
6
a	b	a	b
3	5	5	5
FOUND_ROWS()
8