题解 | #统计salary的累计和running_total#
统计salary的累计和running_total
http://www.nowcoder.com/practice/58824cd644ea47d7b2b670c506a159a6
使用自定义变量求解，使用CONVERT进行格式转换，不然输出会保留3位小数，不知道是为什么
SELECT s.emp_no, s.salary, CONVERT((@summary := @summary + s.salary), SIGNED) running_total FROM salaries s, (SELECT @summary := 0) init WHERE s.to_date = '9999-01-01' ORDER BY s.emp_no
使用窗口函数
SELECT emp_no, salary, SUM(salary) OVER (ORDER BY emp_no) running_total FROM salaries WHERE to_date = '9999-01-01'
