对于所有导致数据库体系结构的业务分析，我建议编写规则：
- 一条路线有2个或更多的车站
- 一个车站可以被许多路线使用
- 路线上的车站按特定顺序排列
您注意到的第一和第二条规则意味着多对多关系，因此您正确地总结了创建routeStation的信息。
第三条规则很有趣。这意味着需要额外的一列才能满足要求。应该去哪里？我们可以看到此属性取决于Route AND Station。因此，它应该位于routeStations中。
我将在表routeStations中添加一列，称为“ stationOrder”。
+-------------+---------------+---------------
| routeId(fk) | stationId(fk) | StationOrder |
+-------------+---------------+---------------
| 1 | 1 | 3 |
+-------------+---------------+---------------
| 1 | 3 | 1 |
+-------------+---------------+---------------
| 1 | 4 | 2 |
+-------------+---------------+---------------
| 2 | 1 | 1 |
+-------------+---------------+---------------
| 2 | 4 | 2 |
+-------------+---------------+---------------
然后查询变得容易：
select rs.routeID,s.Name
from routeStations rs
join
Stations s
on rs.stationId=s.StationId
where rs.routeId=1
order by rs.StationOrder;
+-------------+---------------+
| routeId(fk) | stationId(fk) |
+-------------+---------------+
| 1 | C |
+-------------+---------------+
| 1 | D |
+-------------+---------------+
| 1 | A |
+-------------+---------------+
笔记：
- 我在示例中修复了RouteStation中的StationId。您正在使用StationName作为ID。
- 如果您不使用路线名称，则甚至不需要routeId，因为您可以从routeStations获取该名称。
- 即使您链接到路由表，数据库优化器也会注意到它不需要该额外链接，只需删除这些额外步骤。
为了在注释3上进行开发，我构建了用例：
这是Oracle 12c企业版。
请注意，在下面的执行计划中，根本没有使用表路由。Cost Base Optimizer（CBO）知道它可以直接从routeStations的主键获取routeId（步骤5，ROUTESTATIONS_PK上的INDEX RANGE SCAN，谓词信息5-access（“ RS”。“ ROUTEID” = 1））
--Table ROUTES
create sequence routeId_Seq start with 1 increment by 1 maxvalue 9999999999999 cache 1000;
CREATE TABLE routes
(
routeId INTEGER NOT NULL
);
ALTER TABLE routes ADD (
CONSTRAINT routes_PK
PRIMARY KEY
(routeId)
ENABLE VALIDATE);
insert into routes values (routeId_Seq.nextval);
insert into routes values (routeId_Seq.nextval);
commit;
--TABLE STATIONS
create sequence stationId_seq start with 1 increment by 1 maxvalue 9999999999999 cache 1000;
create table stations(
stationID INTEGER NOT NULL,
name varchar(50) NOT NULL
);
ALTER TABLE stations ADD (
CONSTRAINT stations_PK
PRIMARY KEY
(stationId)
ENABLE VALIDATE);
insert into stations values (stationId_seq.nextval,'A');
insert into stations values (stationId_seq.nextval,'B');
insert into stations values (stationId_seq.nextval,'C');
insert into stations values (stationId_seq.nextval,'D');
commit;
--
--Table ROUTESTATIONS
CREATE TABLE routeStations
(
routeId INTEGER NOT NULL,
stationId INTEGER NOT NULL,
stationOrder INTEGER NOT NULL
);
ALTER TABLE routeStations ADD (
CONSTRAINT routeStations_PK
PRIMARY KEY
(routeId, stationId)
ENABLE VALIDATE);
ALTER TABLE routeStations ADD (
FOREIGN KEY (routeId)
REFERENCES ROUTES (ROUTEID)
ENABLE VALIDATE,
FOREIGN KEY (stationId)
REFERENCES STATIONS (stationId)
ENABLE VALIDATE);
insert into routeStations values (1,1,3);
insert into routeStations values (1,3,1);
insert into routeStations values (1,4,2);
insert into routeStations values (2,1,1);
insert into routeStations values (2,4,2);
commit;
explain plan for select rs.routeID,s.Name
from ndefontenay.routeStations rs
join
ndefontenay.routes r
on r.routeId=rs.routeId
join ndefontenay.stations s
on rs.stationId=s.stationId
where rs.routeId=1
order by rs.StationOrder;
set linesize 1000
set pages 500
select * from table (dbms_xplan.display);
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Plan hash value: 2617709240
---------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 79 | 1 (100)| 00:00:01 |
| 1 | SORT ORDER BY | | 1 | 79 | 1 (100)| 00:00:01 |
| 2 | NESTED LOOPS | | | | | |
| 3 | NESTED LOOPS | | 1 | 79 | 0 (0)| 00:00:01 |
| 4 | TABLE ACCESS BY INDEX ROWID| ROUTESTATIONS | 1 | 39 | 0 (0)| 00:00:01 |
|* 5 | INDEX RANGE SCAN | ROUTESTATIONS_PK | 1 | | 0 (0)| 00:00:01 |
|* 6 | INDEX UNIQUE SCAN | STATIONS_PK | 1 | | 0 (0)| 00:00:01 |
| 7 | TABLE ACCESS BY INDEX ROWID | STATIONS | 1 | 40 | 0 (0)| 00:00:01 |
---------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
5 - access("RS"."ROUTEID"=1)
6 - access("RS"."STATIONID"="S"."STATIONID")
现在有趣的部分，让我们在路由表中添加一个列名。现在在“路线”中实际需要一列。CBO使用索引查找路由1的rowID，然后访问表（通过索引rowid进行表访问）并获取列“ routes.name”。
ALTER TABLE ROUTES
ADD (name VARCHAR2(50));
update routes set name='Old Town' where routeId=1;
update routes set name='North County' where routeId=2;
commit;
explain plan for select r.name as routeName,s.Name as stationName
from routeStations rs
join
routes r
on r.routeId=rs.routeId
join stations s
on rs.stationId=s.stationId
where rs.routeId=1
order by rs.StationOrder;
set linesize 500
set pages 500
select * from table (dbms_xplan.display);
PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------
Plan hash value: 3368128430
----------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 119 | 1 (100)| 00:00:01 |
| 1 | SORT ORDER BY | | 1 | 119 | 1 (100)| 00:00:01 |
| 2 | NESTED LOOPS | | | | | |
| 3 | NESTED LOOPS | | 1 | 119 | 0 (0)| 00:00:01 |
| 4 | NESTED LOOPS | | 1 | 79 | 0 (0)| 00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID| ROUTES | 1 | 40 | 0 (0)| 00:00:01 |
|* 6 | INDEX UNIQUE SCAN | ROUTES_PK | 1 | | 0 (0)| 00:00:01 |
| 7 | TABLE ACCESS BY INDEX ROWID| ROUTESTATIONS | 1 | 39 | 0 (0)| 00:00:01 |
|* 8 | INDEX RANGE SCAN | ROUTESTATIONS_PK | 1 | | 0 (0)| 00:00:01 |
|* 9 | INDEX UNIQUE SCAN | STATIONS_PK | 1 | | 0 (0)| 00:00:01 |
| 10 | TABLE ACCESS BY INDEX ROWID | STATIONS | 1 | 40 | 0 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
6 - access("R"."ROUTEID"=1)
8 - access("RS"."ROUTEID"=1)
9 - access("RS"."STATIONID"="S"."STATIONID")