create table t1 (a int, b int);
insert into t1 values (1,1),(2,2);
explain format=json
select * from t1 where a=name_const('varname',1);
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "cost": "COST_REPLACED",
    "nested_loop": [
      {
        "table": {
          "table_name": "t1",
          "access_type": "ALL",
          "loops": 1,
          "rows": 2,
          "cost": "COST_REPLACED",
          "filtered": 100,
          "attached_condition": "t1.a = 1"
        }
      }
    ]
  }
}
explain format=json
select * from t1 left join t1 as t2 on t1.a=name_const('varname',1) and t1.b=t2.b;
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "cost": "COST_REPLACED",
    "const_condition": "1",
    "nested_loop": [
      {
        "table": {
          "table_name": "t1",
          "access_type": "ALL",
          "loops": 1,
          "rows": 2,
          "cost": "COST_REPLACED",
          "filtered": 100
        }
      },
      {
        "block-nl-join": {
          "table": {
            "table_name": "t2",
            "access_type": "ALL",
            "loops": 2,
            "rows": 2,
            "cost": "COST_REPLACED",
            "filtered": 100
          },
          "buffer_type": "flat",
          "buffer_size": "141",
          "join_type": "BNL",
          "attached_condition": "trigcond(t2.b = t1.b and trigcond(t1.a = 1))"
        }
      }
    ]
  }
}
create table t2 (
a varchar(100) collate utf8_unicode_ci,
b int
);
insert into t2 values ('foo', 1),('bar', 1);
create procedure p1(var1 varchar(10))
update t2 set b=b+1 where a=var1;
call p1('foo');
call p1('foo');
call p1('foo');
select * from t2;
a	b
foo	4
bar	1
create table t3 (
a varchar(100) collate utf8_unicode_ci,
b int
);
insert into t3 values ('foo', 1),('bar', 1);
select * from t3;
a	b
foo	1
bar	1
explain format=json
update t3 set b=b+1 where a= NAME_CONST('var1',_latin1'foo' COLLATE 'latin1_swedish_ci');
EXPLAIN
{
  "query_block": {
    "select_id": 1,
    "table": {
      "update": 1,
      "table_name": "t3",
      "access_type": "ALL",
      "rows": 2,
      "attached_condition": "t3.a = convert(_latin1'foo' collate latin1_swedish_ci using utf8mb3)"
    }
  }
}
select * from t3 where a= NAME_CONST('var1',_latin1'foo' COLLATE 'latin1_swedish_ci');
a	b
foo	1
drop procedure p1;
drop table t1, t2, t3;