@a - connection_id()
3
i
1
2
i	@vv1:=if(sv1.i,1,0)	@vv2:=if(sv2.i,1,0)	@vv3:=if(sv3.i,1,0)	@vv1+@vv2+@vv3
1	1	0	1	2
2	1	0	0	1
table	type	possible_keys	key	key_len	ref	rows	Extra
t1	ref	i	i	4	const	1	where used
table	type	possible_keys	key	key_len	ref	rows	Extra
t1	ALL	NULL	NULL	NULL	NULL	3	where used
table	type	possible_keys	key	key_len	ref	rows	Extra
t1	index	NULL	i	4	NULL	3	where used; Using index
table	type	possible_keys	key	key_len	ref	rows	Extra
t1	ref	i	i	4	const	1	where used
@a:=10	@b:=1	@a > @b	@a < @b
10	1	1	0
@a:="10"	@b:="1"	@a > @b	@a < @b
10	1	1	0
@a:=10	@b:=2	@a > @b	@a < @b
10	2	1	0
@a:="10"	@b:="2"	@a > @b	@a < @b
10	2	0	1