How to count the number of identical values ​​and divide the field values ​​by this number?

Question

SQL

Good day to all. Tell me please.
for example, there is a table table1
Number Amount
1 156 1
2 256 7
3 256 7
I need to find out how many rows with the same values, and display the Amount divided by the number of these values.
Help me please.

Answer 1

groupby + avg() +count()