如何将月列和年列连接到年月列

Question

I have an SQL table with columns (month, year, and yearmonth)

Month    year    
 5       2020
 6       2020
 11      2020

I want to insert yearmonth column values in this format

yearmonth
   202005
   202006
   202011

I've tried couple of Datetime functions, but it didn't work.

Answer 1

I think that it is simpler to use string functions:

select t.*, concat(year, lpad(month, 2, '0')) as yearmonth
from mytable t

lpad() adds the "missing" 0 to the month part if needed, which you can then concatenate with the year.

On the other hand, if you want a numeric result, arithmetics is the way to go:

select t.*, year * 100 + month as yearmonth
from mytable t

Answer 2

如果你想要一个字符串，我可能会使用：

select cast(year * 100 + month as char)