在第三张表中联接两个表数据

Question

I have two tables ,one sensor_info and other one is bays_info.here are the tables

id  Sensor_Name   stn_id    value  Station_id
1   Sensor1          0       4.4      1
2   Sensor2          0       2.1      1
3   Sensor3          0       3.2      1
4   Sensor4          1       4.5      1 

Bays_info

gate_id     bay_name    bay_status    Station_id  

GATE1       B_gate1         1            1
GATE2       B_gate2        -999          1
GATE3       B_gate2         1            1
GATE4       B_gate2        -999          1
GATE5       B_gate2          1           1

Friends I need to show all "sensors value" for each gate, like below (here station id is common col)

gate_id     bay_name    bay_status    Station_id  Sensor1  Sensor2 sensor3 sensor4

GATE1       B_gate1         1            1         4.4       2.1    3.2      4.5
GATE2       B_gate2        -999          1         4.4       2.1    3.2      4.5
GATE3       B_gate2         1            1         4.4       2.1    3.2      4.5
GATE4       B_gate2        -999          1         4.4       2.1    3.2      4.5
GATE5       B_gate2          1           1         4.4       2.1    3.2      4.5

So I need to show value from sensor table for each station and also need to show sensor names as header.Please help me for MySQL query.

Answer 1

try this

   select gate_id  ,   bay_name ,   bay_status  ,  bays_info.Station_id,
   max(case when Sensor_Name = 'US.SEN1' then round(value,2) end) as Sensor1,
   max(case when Sensor_Name = 'US.SEN2' then round(value,2) end) as Sensor2,
   max(case when Sensor_Name = 'US.SEN3' then round(value,2) end) as Sensor3,
   max(case when Sensor_Name = 'DS.SEN1' then round(value,2) end) as Sensor4,
   max(case when Sensor_Name = 'DS.SEN2' then round(value,2) end) as Sensor5,
   max(case when Sensor_Name = 'DS.SEN3' then round(value,2) end) as Sensor6,
   max(case when Sensor_Name = 'MS.SEN1' then round(value,2) end) as Sensor7
   from bays_info
   inner join sensor_info 
   on sensor_info.Station_id = bays_info.Station_id
   group by gate_id

DEMO HERE