查询选择所有记录并计算相同的值？

Question

此表：

name | city
 --------
john   na
mary   ny
mary   in

是否存在返回所有记录和计数名称重复的查询？

查询结果：

name | count(name)
 john   1
 mary   2
 mary   2

由于

Answer 1

select o.name "Name", 
   (select count(*) from table_name i where i.name = o.name) "Count"
from table_name o;

Answer 2

如果您的RDBMS支持窗口聚合函数。

SELECT name, 
       COUNT(*) OVER (PARTITION BY name)
FROM YourTable

Answer 3

SELECT name,
 COUNT(name) AS cnt
FROM table_name
GROUP BY name;