いずれのDBも内部結合への自動変換をサポートしている模様
(8.0.29)
drop table tab1;
create table tab1(
col1 bigint primary key
,col2 bigint
);
drop table tab2;
create table tab2(
col1 bigint primary key
,col2 bigint
);
drop procedure proc1;
delimiter //
create procedure proc1(in x int)
begin
declare i int;
set i = 0;
start transaction;
while i < x do
set i = i + 1;
insert into tab1 values(
i
,i
);
insert into tab2 values(
i
,i
);
end while;
commit;
end
//
delimiter ;
call proc1(1000000);
analyze table tab1;
analyze table tab2;
explain format=tree
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t1.col2 = 123
;
explain format=tree
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t2.col2 = 123
;
外部結合されるテーブルに非ヌル条件がある場合、内部結合となる
(19c)
drop table tab1 purge;
create table tab1(
col1 int constraint tab1pk primary key
,col2 int
);
drop table tab2 purge;
create table tab2(
col1 int constraint tab2pk primary key
,col2 int
);
declare
begin
for i in 1..1000000 loop
insert into tab1 values(
i
,i
);
insert into tab2 values(
i
,i
);
end loop;
end;
/
commit;
set time on
set timing on
exec dbms_stats.gather_table_stats(user,'TAB1');
exec dbms_stats.gather_table_stats(user,'TAB2');
explain plan for
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t1.col2 = 123
;
select * from table(dbms_xplan.display(format=>'ALL') );
explain plan for
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t2.col2 = 123
;
select * from table(dbms_xplan.display(format=>'ALL') );
外部結合されるテーブルに非ヌル条件がある場合、内部結合となる
(14)
drop table tab1 cascade;
create table tab1(
col1 bigint constraint tab1pk primary key
,col2 bigint
);
drop table tab2 cascade;
create table tab2(
col1 bigint constraint tab2pk primary key
,col2 bigint
);
start transaction;
insert into tab1 select
g
,g
from generate_series(1,1000000) g;
commit;
start transaction;
insert into tab2 select
g
,g
from generate_series(1,1000000) g;
commit;
\timing 1
\pset pager 0
analyze tab1;
analyze tab2;
explain analyze
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t1.col2 = 123
;
explain analyze
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t2.col2 = 123
;
外部結合されるテーブルに非ヌル条件がある場合、内部結合となる
(2019)
drop table tab1;
create table tab1(
col1 bigint not null constraint tab1pk primary key
,col2 bigint
);
drop table tab2;
create table tab2(
col1 bigint not null constraint tab2pk primary key
,col2 bigint
);
set nocount on
declare @i int;
set @i = 1;
begin transaction;
while @i <= 1000000
begin
insert into tab1 values(
@i
,@i
);
insert into tab2 values(
@i
,@i
);
set @i = @i + 1;
end
commit;
update statistics tab1;
update statistics tab2;
set statistics time on
set showplan_all on
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t1.col2 = 123
;
select
t1.col1 col11
,t1.col2 col12
,t2.col2 col22
from tab1 t1 left join tab2 t2
on t1.col1 = t2.col1
where t2.col2 = 123
;
外部結合されるテーブルに非ヌル条件がある場合、内部結合となる
