MySQL - 列出多个属性

Question

我的数据库中有两个表：AppropriateFor和AquariumModel，如下所示。它们共享三个键 - AquariumType，Salinity和Volume。我试图找到适合多种物种的所有水族馆模型。我试图正确计算AppropriateFor中的主要元组，然后将其与AquariumModel表连接起来。

AppropriateFor表有四列：speciesName，aquariumType，salinity，volume：

RED-BELLIED PACU                AGGRESSIVE  FRESHWATER  300
GOLDEN MORAY EEL            AGGRESSIVE  MARINE      25000
NURSE SHARK                 AGGRESSIVE  MARINE      25000
COMMON TOADFISH             COMMUNITY   BRACKISH    150
DRAGON GOBY                 COMMUNITY   BRACKISH        150
BRONZE CORYDORAS            COMMUNITY   FRESHWATER  250
COMMON DISCUS               COMMUNITY   FRESHWATER  250
SPOTTED RAPHAEL             COMMUNITY   FRESHWATER  250
UPSIDE-DOWN CATFISH         COMMUNITY   FRESHWATER  250
BLUESPOTTED ANGELFISH       COMMUNITY   MARINE      50000
CHALK BASS                  COMMUNITY   MARINE      50000
FLAME ANGELFISH             COMMUNITY   MARINE      50000
ORIENTAL SWEETLIPS          COMMUNITY   MARINE      50000
ROUND STINGRAY              COMMUNITY   MARINE      50000
ROYAL ANGELFISH             COMMUNITY   MARINE      50000
TEIRA BATFISH               COMMUNITY   MARINE      50000
BARTLETTS ANTHIAS           REEF        MARINE      75000
BELLUS ANGELFISH            REEF        MARINE      75000
CHALK BASS                  REEF        MARINE      75000
COPPERBANDED BUTTERFLYFISH  REEF        MARINE      75000
MANDARINFISH                    REEF        MARINE      75000
COMMON TOADFISH             SPECIES     BRACKISH    100
GREEN SPOTTED PUFFER        SPECIES     BRACKISH    100
REEDFISH                    SPECIES     BRACKISH        100
ELECTRIC EEL                    SPECIES     FRESHWATER  500
ORNATE BICHIR               SPECIES     FRESHWATER  500
REEDFISH                    SPECIES     FRESHWATER  500
BRAZILIAN SEAHORSE          SPECIES     MARINE      10000

AquariumModel也有四列：aquariumType，salinity，volume，price：

AGGRESSIVE  BRACKISH    125    200
AGGRESSIVE  FRESHWATER  300    500
AGGRESSIVE  MARINE      25000  4500
COMMUNITY   BRACKISH    150    250
COMMUNITY   FRESHWATER  250    400
COMMUNITY   MARINE      50000  7000
REEF        MARINE      75000  10000
SPECIES     BRACKISH    100    150
SPECIES     FRESHWATER  500    800
SPECIES     MARINE      10000  3000

Answer 1

我认为你可以从两个表一起加入你需要的值，这将从这样开始：

SELECT * 
FROM aquariummodel am 
JOIN appropriatefor af ON am.aquariumtype = af.aquariumtype AND am.salinity = af.salinity AND am.volume = af.volume;

然后，您想要按水族箱类型中的所有值进行分组，并使用计数大于1的条件。所以我会将查询更改为：

SELECT am.*, COUNT(*) AS numFishAppropriateFor
FROM aquariummodel am
JOIN appropriatefor af ON am.aquariumtype = af.aquariumtype AND am.salinity = af.salinity AND am.volume = af.volume
GROUP BY am.aquariumtype, am.salinity, am.volume
HAVING COUNT(*) > 1;

修改 这是一个SQL Fiddle来证明它有效。

如果可以的话，我想评论一下你的数据库的设计。

在适当的表中，您有几个从水族模型表重复的列。我会在你的aquariummodel表中添加一个主键（比如auto_increment id），并在适当的表中使用该id。这样，aquariummodel将有5列，但适合可以减少到两列：speciesname和aquariummodel_id。只是一个建议。