如何在 PSQL 中查询 3 个表？

Question

我是数据库新手，我不知道如何查询这 3 个表。

我试图找出过去 1 年（表 - 时间？）每种菌株（表菌株）的总死亡人数（表 COVID - TotalDeathUK）

表COVID

 centerid | patientid | dateid | strainid | totaldeathsuk | 
----------+-----------+--------+----------+---------------+
   100000 |    100000 | 100000 |   100000 |         31369 |       
   100000 |    100000 | 100000 |   100000 |         95382 |       
   100004 |    100004 | 100004 |   100000 |         46031 |

----------------------------------------------------------------

表应变

 strainid |   name    | risk 
----------+-----------+------
   100000 | Fixflex   |   50
   100001 | Cardguard |   85
   100002 | Zaam-Dox  |   53

餐桌时间

 dateid | year |    month     | quater | week | dayofweek |   hour   
--------+------+--------------+--------+------+-----------+----------
 100007 | 2039 | Thin Ice     |      2 |    3 |         7 | 11:54:00
 100008 | 2109 | Parineeta    |      4 |    1 |         6 | 20:12:00
 100011 | 2096 | Crawlspace   |      4 |    2 |         7 | 19:03:00

链接到数据库模式的图像

Answer 1

 CREATE TABLE Covid(CenterID int,PatientID int, DateID int,StrainID int,TotalDeathUK int); CREATE TABLE Strain(StrainID int, Name varchar(20),Risk int); CREATE TABLE Time(DateID int,Year int,Month varchar(20),Quarter int,Week int,DayOfWeek int,Hour varchar(8))

 INSERT INTO Covid(CenterID,PatientID, DateID,StrainID,TotalDeathUK) VALUES(100000,100000,100000,100000,31369), (100000,100000,100008,100000,95382), (100004,100004,100011,100000,46031); INSERT INTO Strain(StrainID, Name,Risk) VALUES( 100000,'Fixflex ',50),( 100001,'Cardguard ',85),( 100002,'Zaam-Dox ',53); INSERT INTO Time(DateID,Year,Month,Week,Quarter,DayOfWeek,Hour)VALUES(100000,2020,'Thin Ice',2,3,7,'11:54:00'), (100008,2019,'Parineeta',4,1,6,'20:12:00'), (100011,2018,'Crawlspace',4,2,7,'19:03:00');

 SELECT T.Year,S.StrainID,C.TotalDeathUK FROM Covid AS C LEFT JOIN Strain AS S ON S.StrainID=C.StrainID LEFT JOIN Time AS T ON T.DateID=C.DateID WHERE T.Year=date_part('year', (SELECT current_timestamp))-1

 年份 | 应变ID | 完全死亡 ---: |  --------: |  ------------: 2020 |  100000 |  31369

db<> 在这里摆弄