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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;
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