场景:
基础知识查询.
环境:
Oracle Database 11g; PL/SQL Developer
1.表数据
1.1 传感器采集区域 sensor_collect_region
1.2 传感器采集数据 sensor_collect_data
2. join
两张表根据on条件进行连接查询,查询出两张表完全匹配的结果集.
select *
from sensor_collect_data aa
join sensor_collect_region bb
on aa.region = bb.region
3. left join (左连接)
两张表根据on条件进行左连接查询,会返回left join左边表所有行,即使右表没有匹配记录.
select *
from sensor_collect_data aa
left join sensor_collect_region bb
on aa.region = bb.region
4. right join (右连接)
两张表根据on条件进行右连接查询,会返回right join右边表所有行,即使左表没有匹配记录.
select *
from sensor_collect_data aa
right join sensor_collect_region bb
on aa.region = bb.region
5. inner join (内连接)
两张表根据on条件进行内连接查询,查询出两张表完全匹配的结果集.
select *
from sensor_collect_data aa
inner join sensor_collect_region bb
on aa.region = bb.region
6. full join (全连接)
两张表根据on条件进行连接查询,返回左表和右表中所有记录,包括没有匹配的记录.
select *
from sensor_collect_data aa
full join sensor_collect_region bb
on aa.region = bb.region
7. left outer join
与left join相同
select *
from sensor_collect_data aa
left outer join sensor_collect_region bb
on aa.region = bb.region
8. right outer join
right join 相同
select *
from sensor_collect_data aa
right outer join sensor_collect_region bb
on aa.region = bb.region
9. 左连接和右连接进行union操作
select *
from sensor_collect_data aa
left join sensor_collect_region bb
on aa.region = bb.region
union
select *
from sensor_collect_data aa
right join sensor_collect_region bb
on aa.region = bb.region
10. 结论
join和inner join等价
left join和left outer join等价
right join和right outer join等价
left join与right join进行union操作和full join等价
11.附建表语句
11.1 建表语句一
create table SENSOR_COLLECT_DATA
(
sensor_id NUMBER(16) not null,
region VARCHAR2(16) not null,
s1 NUMBER(6,3),
s2 NUMBER(6,3),
s3 NUMBER(6,3)
);
comment on table SENSOR_COLLECT_DATA
is '传感器采集数据';
comment on column SENSOR_COLLECT_DATA.sensor_id
is '数据id实体唯一标识';
comment on column SENSOR_COLLECT_DATA.region
is '传感器安装区域';
comment on column SENSOR_COLLECT_DATA.s1
is '传感器采集的值1';
comment on column SENSOR_COLLECT_DATA.s2
is '传感器采集的值2';
comment on column SENSOR_COLLECT_DATA.s3
is '传感器采集的值3';
insert into SENSOR_COLLECT_DATA (sensor_id, region, s1, s2, s3)
values (20191502, '2019', 12, 33, 55);
insert into SENSOR_COLLECT_DATA (sensor_id, region, s1, s2, s3)
values (20191514, '2018', 22, 33, 5);
insert into SENSOR_COLLECT_DATA (sensor_id, region, s1, s2, s3)
values (20191513, '2018', 2, 3, 66);
insert into SENSOR_COLLECT_DATA (sensor_id, region, s1, s2, s3)
values (20191515, '2028', 8, 56, 77);
insert into SENSOR_COLLECT_DATA (sensor_id, region, s1, s2, s3)
values (20191517, '2017', 22, 33, 33);
insert into SENSOR_COLLECT_DATA (sensor_id, region, s1, s2, s3)
values (20191516, '2017', 22.22, 33.33, 55.33);
insert into SENSOR_COLLECT_DATA (sensor_id, region, s1, s2, s3)
values (20191501, '2019', 12.88, 888.55, 3.22);
commit;
11.2 建表语句二
create table sensor_collect_region
(
region VARCHAR2(16) not null,
region_name VARCHAR2(128),
region_type VARCHAR2(128)
);
comment on table sensor_collect_region
is '传感器采集区域';
comment on column sensor_collect_region.region
is '传感器安装区域,实体唯一标识';
comment on column sensor_collect_region.region_name
is '名称';
comment on column sensor_collect_region.region_type
is '类型';
insert into SENSOR_COLLECT_REGION (region, region_name, region_type)
values ('2017', '江苏', '1');
insert into SENSOR_COLLECT_REGION (region, region_name, region_type)
values ('2018', '福建', '2');
insert into SENSOR_COLLECT_REGION (region, region_name, region_type)
values ('2019', '浙江', '1');
insert into SENSOR_COLLECT_REGION (region, region_name, region_type)
values ('2016', '黑龙江', '3');
commit;
以上,感谢.