planen
Einrichtung
create table users
(
id integer primary key not null,
username varchar(23) not null
-- some user data..
);
create table setting_types
(
id integer primary key not null,
name varchar(23) not null
);
create table user_settings
(
id integer primary key not null,
user_id integer not null,
setting_type_id integer not null,
value varchar(13) not null,
foreign key ( user_id ) references users( id ),
foreign key ( setting_type_id ) references setting_types ( id )
);
insert into users
( id, username )
values
( 1, 'Admin' ),
( 2, 'heresjonny' )
;
insert into setting_types
( id, name )
values
( 1, 'setting_type_1' ),
( 2, 'setting_type_2' ),
( 3, 'setting_type_3' ),
( 4, 'setting_type_4' ),
( 5, 'setting_type_5' ),
( 6, 'setting_type_6' ),
( 7, 'setting_type_7' ),
( 8, 'setting_type_8' )
;
insert into user_settings
( id, user_id, setting_type_id, value )
values
( 1, 1, 1, 'true' ),
( 2, 1, 2, 'false' ),
( 3, 1, 3, 'false' ),
( 4, 1, 4, 'false' ),
( 5, 2, 3, 'true' ),
( 6, 2, 4, 'true' ),
( 7, 2, 5, 'false' ),
( 8, 2, 6, 'true' ),
( 9, 2, 7, 'true' ),
( 10, 2, 8, 'true' )
;
Drehpunkt
set @pivot_source = '(
select st.id as setting_id, st.name, users.id as user_id, users.username, coalesce(us.value, ''false'') as value
from setting_types st
cross join
(
select id, username
from users
) users
left join user_settings us
on users.id = us.user_id
and st.id = us.setting_type_id
)';
set @pivot_sql := replace('
select user_id, username,
#setting_aliases#
from
(
select #first_user_dets#,
#settings_fields#
from
#pivot_source# #first_alias#
inner join
#all_joins#
) q
order by user_id
;', '#pivot_source#', @pivot_source);
set @pivot_block := replace('
#pivot_source# #alias#
on #last_alias#.user_id = #alias#.user_id
and #last_alias#.setting_id < #alias#.setting_id
inner join #all_joins#', '#pivot_source#', @pivot_source)
;
select count(*) into @ignore
from
(
select
@pivot_sql := replace(@pivot_sql, '#all_joins#', replace(replace(@pivot_block, '#alias#', concat('sett', right_id)), '#last_alias#', concat('sett', left_id)))
from
(
select `left`.id as left_id, min(`right`.id) as right_id
from setting_types `left`
inner join setting_types `right`
on `left`.id < `right`.id
group by 1
) t
order by left_id
) `ignore`
;
select concat('sett', id) into @first_alias
from setting_types
order by id
limit 1
;
select concat(@first_alias, '.user_id,',@first_alias,'.username') into @first_user_dets;
select group_concat(concat('sett', id, '.value ', name) SEPARATOR ',') into @settings_fields
from setting_types
;
select group_concat(name SEPARATOR ',') into @setting_aliases
from setting_types
;
select count(*) into @ignore
from
(
select
@pivot_sql := replace(@pivot_sql, '#first_user_dets#', @first_user_dets),
@pivot_sql := replace(@pivot_sql, '#settings_fields#', @settings_fields),
@pivot_sql := replace(@pivot_sql, '#setting_aliases#', @setting_aliases),
@pivot_sql := replace(@pivot_sql, '#first_alias#', @first_alias),
@pivot_sql := replace(@pivot_sql, 'inner join #all_joins#', '')
) `ignore`
;
select @pivot_sql;
prepare pivot_sql from @pivot_sql;
EXECUTE pivot_sql;
deallocate prepare pivot_sql;
Ausgabe
+---------+------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| user_id | username | setting_type_1 | setting_type_2 | setting_type_3 | setting_type_4 | setting_type_5 | setting_type_6 | setting_type_7 | setting_type_8 |
+---------+------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 1 | Admin | true | false | false | false | false | false | false | false |
| 2 | heresjonny | false | false | true | true | false | true | true | true |
+---------+------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
Hinweis
Es ist üblicher, dieses Pivotieren im Anwendungscode durchzuführen. Wenn Ihr Grund dafür die Leistung ist, sollten Sie dies mit dem analogen Pivotieren in PHP vergleichen, um zu testen, ob es tatsächlich deutlich besser ist..
könnte meine frühere Antwort auf schwenkbar mit dynamischen Säulen nützlich für die Entwicklung Ihres PHP-Codes zum Benchmarking der Leistung
