查找分配给另一个字段值的计数

Question

Create table t1 (col1 (number), col2 (number), col3 (number);

Insert into t1 values (1,1,1);
Insert into t1 values (1,2,5);
Insert into t1 values (1,3,1);
Insert into t1 values (2,1,1);
Insert into t1 values (2,1,1);

Desired result
 col1  col2
  1     3
  2     2

我需要返回col1中的值以及col 2中为每个不同col1值找到的值的计数。不需要col3

Answer 1

select col1, count(col1) from t1
group by col1