我想将几个表与另一个表连接起来，但结果返回了0行

Question

我的EER Modell图像。

我必须做一个小节和一个内部连接吗？我的查询

SELECT mounting_system_type, positions.id , positions.module_count as mp, configurations.position_id, module_blocks.id ,module_blocks.module_count as Anzahl_pro_Block,
ballast as ballast_pro_Modulblock, dead_weight as EGG_pro_Block, dead_load as pro_Block, obstacles.height,
obstacles.module_area_offset, obstacles.shape_type, roof_zone
FROM base.positions
join configurations on positions.id = configurations.position_id
join module_blocks on configurations.id = module_blocks.configuration_id
join roof_zones on configurations.id = roof_zones.configuration_id
join obstacles on positions.id = obstacles.position_id
group by module_blocks.id

Answer 1

首先，没有FROM base.positions这样的东西，您可以指定一个表FROM positions。

你可以在这里阅读有关JOIN的信息。您只需要添加字段，而不指定字段的来源。下次还提供一个您得到的错误。

SELECT positions.mounting_system_type, positions.id , positions.module_count as mp, configurations.position_id, module_blocks.id ,module_blocks.module_count as Anzahl_pro_Block,
module_blocks.ballast as ballast_pro_Modulblock, module_blocks.dead_weight as EGG_pro_Block, module_blocks.dead_load as pro_Block, obstacles.height,
obstacles.module_area_offset, obstacles.shape_type, roof_zone.roof_zone
FROM positions
join configurations on positions.id = configurations.position_id
join module_blocks on configurations.id = module_blocks.configuration_id
join roof_zones on configurations.id = roof_zones.configuration_id
join obstacles on positions.id = obstacles.position_id
group by module_blocks.id

如果您想要的roof_zone来自module_fields_roof_分区表(您在两个表中有roof_zone(：

SELECT positions.mounting_system_type, positions.id , positions.module_count as mp, configurations.position_id, module_blocks.id ,module_blocks.module_count as Anzahl_pro_Block,
module_blocks.ballast as ballast_pro_Modulblock, module_blocks.dead_weight as EGG_pro_Block, module_blocks.dead_load as pro_Block, obstacles.height,
obstacles.module_area_offset, obstacles.shape_type, module_fields_roof_zones.roof_zone
FROM positions
join configurations on positions.id = configurations.position_id
join module_blocks on configurations.id = module_blocks.configuration_id
join roof_zones on configurations.id = roof_zones.configuration_id
join module_fields_roof_zones on configurations.id = module_fields_roof_zones.configuration_id
join obstacles on positions.id = obstacles.position_id
group by module_blocks.id

试试这个，看看是否有任何错误或结果。