How could I split one row into multiple rows?

Question

So, I have this table

col1
1,2,3
1,4,5

and I want it to be like this

col1
1
2
3
1
4
5

Answer 1

You can split string like this:

SELECT 
    value  
FROM 
    STRING_SPLIT('a,b,c', ',');

Answer 2

It seems your delimited data is in a column. If so, you can use string_split() in concert with a CROSS APPLY

 Select col1=B.value
  From  YourTable A
  Cross Apply string_split(A.col1,',') B