set @`test`=1,@TEST=3,@select=2,@t5=1.23456;
select @test,@`select`,@TEST,@not_used;
@test	@`select`	@TEST	@not_used
1	2	3	NULL
set @test_int=10,@test_double=1e-10,@test_string="abcdeghi",@test_string2="abcdefghij",@select=NULL;
select @test_int,@test_double,@test_string,@test_string2,@select;
@test_int	@test_double	@test_string	@test_string2	@select
10	1e-10	abcdeghi	abcdefghij	NULL
set @test_int="hello",@test_double="hello",@test_string="hello",@test_string2="hello";
select @test_int,@test_double,@test_string,@test_string2;
@test_int	@test_double	@test_string	@test_string2
hello	hello	hello	hello
set @test_int="hellohello",@test_double="hellohello",@test_string="hellohello",@test_string2="hellohello";
select @test_int,@test_double,@test_string,@test_string2;
@test_int	@test_double	@test_string	@test_string2
hellohello	hellohello	hellohello	hellohello
set @test_int=null,@test_double=null,@test_string=null,@test_string2=null;
select @test_int,@test_double,@test_string,@test_string2;
@test_int	@test_double	@test_string	@test_string2
NULL	NULL	NULL	NULL
select @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3;
@t1:=(@t2:=1)+@t3:=4	@t1	@t2	@t3
5	5	1	4
select @t5;
@t5
1.23456