Si vous voulez toutes les lignes (sortie en bloc) et non une ligne à la fois, ce qui suit doit être rapide et la sortie pour toutes les lignes contiendra toutes les colonnes.
Considérons ci-dessous les champs des tables.obj_mobiles - ID | M1 | M2obj_tablets - ID | T1 | T2obj_computers - ID | C1 | C2objects - ID | taper | nom | etc.,
Select objects.*, typestable.*
from (
select ID as oID, "mobile" as otype, M1, M2, NULL T1, NULL T2, NULL C1, NULL C2 from obj_mobiles
union all
select ID as oID, "tablet" as otype, NULL, NULL, T1, T2, NULL, NULL from obj_tablets
union all
select ID as oID, "computer" as otype, NULL, NULL, NULL, NULL, C1, C2 from obj_computers) as typestable
left join objects on typestable.oID = objects.ID and typestable.otype = objects.type;
+------+--------------------+----------+------+----------+------+------+------+------+------+------+
| ID | name | type | ID | type | M1 | M2 | T1 | T2 | C1 | C2 |
+------+--------------------+----------+------+----------+------+------+------+------+------+------+
| 1 | Samsung Galaxy s2 | mobile | 1 | mobile | 1 | Thin | NULL | NULL | NULL | NULL |
| 2 | Samsung Galaxy Tab | tablet | 2 | tablet | NULL | NULL | 0.98 | 10 | NULL | NULL |
| 3 | Dell Inspiron | computer | 3 | computer | NULL | NULL | NULL | NULL | 4.98 | 1000 |
+------+--------------------+----------+------+----------+------+------+------+------+------+------+
Le tableau est créé comme ci-dessous.
mysql> create table objects (ID int, name varchar(50), type varchar (15));
Query OK, 0 rows affected (0.05 sec)
mysql> insert into objects values (1, "Samsung Galaxy s2", "mobile"), (2, "Samsung Galaxy Tab", "tablet"), (3, "Dell Inspiron", "computer");
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> create table obj_mobiles (ID int, M1 int, M2 varchar(10));
Query OK, 0 rows affected (0.03 sec)
mysql> insert into obj_mobiles values (1, 0.98, "Thin");
Query OK, 1 row affected (0.00 sec)
mysql> create table obj_tablets (ID int, T1 float, T2 int(10));
Query OK, 0 rows affected (0.03 sec)
mysql> insert into obj_tablets values (2, 0.98, 10);
Query OK, 1 row affected (0.00 sec)
mysql> create table obj_computers (ID int, C1 float, C2 int(10));
Query OK, 0 rows affected (0.03 sec)
insert into obj_computers values (3, 4.98, 1000);
également pour confirmer que les types de données des colonnes sont les mêmes que les colonnes d'origine, le résultat est enregistré dans une table et les types de données sont vérifiés ci-dessous.
create table temp_result as
Select objects.*, typestable.*
from (
select ID as oID, "mobile" as otype, M1, M2, NULL T1, NULL T2, NULL C1, NULL C2 from obj_mobiles
union all
select ID as oID, "tablet" as otype, NULL, NULL, T1, T2, NULL, NULL from obj_tablets
union all
select ID as oID, "computer" as otype, NULL, NULL, NULL, NULL, C1, C2 from obj_computers) as typestable
left join objects on typestable.oID = objects.ID and typestable.otype = objects.type;
mysql> desc temp_result;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| ID | int(11) | YES | | NULL | |
| name | varchar(50) | YES | | NULL | |
| type | varchar(15) | YES | | NULL | |
| oID | int(11) | YES | | NULL | |
| otype | varchar(8) | NO | | | |
| M1 | int(11) | YES | | NULL | |
| M2 | varchar(10) | YES | | NULL | |
| T1 | float | YES | | NULL | |
| T2 | int(11) | YES | | NULL | |
| C1 | float | YES | | NULL | |
| C2 | int(11) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
11 rows in set (0.00 sec)
