如何在 SQL 中的 3 个不同表中加入一个低于另一个（不融合/合并数据）的 3 列？

Question

On Pentaho - Spoon I want to select and join 3 columns which are fields related to Date and named differently, from 3 different tables (one field from each table), and join all the data in one single column that will be called Date. I tried to do it with a step but couldn't find it so I think the easiest way is to write the script. Any idea? I am lost...Thanks!!

I started with: SELECT dbo.SCHOOL.Date, dbo.STUDENT.Year, dbo.EXAMS.Year FROM dbo.SCHOOL, dbo.STUDENT, dbo.EXAMS

Answer 1

use UNION not JOIN, if you want to merge data. If your all columns have the same data type (date).

SELECT Date, 'SchoolTable' FROM dbo.School
    UNION  
SELECT Year, 'StudentTable' FROM dbo.Student
    UNION
SELECT Year, 'ExamsTable' FROM dbo.Exams

or give more information about tables