func_str.result:

select charset(null), collation(null), coercibility(null);

charset(null)	collation(null)	coercibility(null)

binary	binary	5

CREATE TABLE t1 (a int, b int);

CREATE TABLE t2 (a int, b int);

INSERT INTO t1 VALUES (1,1),(2,2);

INSERT INTO t2 VALUES (2,2),(3,3);

select t1.*,t2.* from t1 left join t2 on (t1.b=t2.b)

where collation(t2.a) = _utf8'binary' order by t1.a,t2.a;

a	b	a	b

1	1	NULL	NULL

2	2	2	2

select t1.*,t2.* from t1 left join t2 on (t1.b=t2.b)

where charset(t2.a) = _utf8'binary' order by t1.a,t2.a;

a	b	a	b

1	1	NULL	NULL

2	2	2	2

select t1.*,t2.* from t1 left join t2 on (t1.b=t2.b)

where coercibility(t2.a) = 2 order by t1.a,t2.a;

a	b	a	b

1	1	NULL	NULL

2	2	2	2

DROP TABLE t1, t2;

select SUBSTR('abcdefg',3,2);

SUBSTR('abcdefg',3,2)

cd