How can I add a character into a specified position into string in SQL SERVER?

Question

I have a varchar field like:

195500
122222200

I need to change these values to:

1955.00
1222222.00

Answer 1

try this

Declare @s varchar(50) = '1234567812333445'
Select Stuff(@s, Len(@s)-1, 0, '.')
--> 12345678123334.45

fiddle demo