SQL 基于多个日期列创建最小日期列的代码

Question

我有一个包含多个日期列的 SQL table，其中一些是空白的 (Example of Table) and I want to create a column in SQL that calculates the earliest date across the 3 columns (Expected Output)

任何帮助将不胜感激！

Answer 1

请始终提及带有版本的数据库名称以获得更好的解决方案。

架构和插入语句：

 create table Patients (Patient varchar(50), Doctor_Date date, Nurse_Date date, Physio_Date date);

 insert into Patients (Patient,Doctor_Date)values ('Patient 1','26/11/2021');
 insert into Patients (Patient,Doctor_Date,Nurse_Date,Physio_Date) values('Patient 2','17/11/2021','20/11/2021','16/11/2021');
 insert into Patients (Patient,Nurse_Date,Physio_Date) values('Patient 3','5/12/2021','4/05/2021');

查询：

  select Patient, 
              (SELECT MIN(mindate) FROM (VALUES (Doctor_Date), (Nurse_Date), (Physio_Date)) AS X(mindate)) AS Minimum_Date
  from Patients

输出：

patient	minimum_date
Patient 1	2021-11-26
Patient 2	2021-11-16
Patient 3	2021-05-04

db<>fiddle here

SQL 基于多个日期列创建最小日期列的代码

SQL code to create min date column based on multiple date columns

sql

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