使用oracle来计算方差及标准差

/* Formatted on 5/24/2012 4:15:58 PM (QP5 v5.149.1003.31008) */
SELECT deptno,
      ename,                     --st_name || ' ' || last_name employee_name,
      hiredate,
     sal,
       STDDEV (sal) OVER (PARTITION BY deptno ORDER BY hiredate) AS "STDDEV", --标准差
       STDDEV_SAMP (sal) OVER (PARTITION BY deptno ORDER BY hiredate)
          AS "STDDEV_SAMP",                                            --样本标准差
       VAR_POP (sal) OVER (PARTITION BY deptno ORDER BY hiredate)    说明：VAR_POP 为函数， sal为要求的数据列，  以‘deptno’为分组的根据，即满足这个条件下才进行方差的操作，最后根据‘hiredate’进行排序。
          AS "VAR_POP",                                                   --方差
       VAR_SAMP (sal) OVER (PARTITION BY deptno ORDER BY hiredate)
          AS "VAR_SAMP"                                                 --样本方差
  FROM scott.emp
 WHERE deptno IN (20);
 
 /* Formatted on 5/24/2012 4:15:58 PM (QP5 v5.149.1003.31008) */
SELECT deptno,
       STDDEV (sal)  AS "STDDEV", --标准差
       STDDEV_SAMP (sal)
          AS "STDDEV_SAMP",                                            --样本标准差
       VAR_POP (sal)
          AS "VAR_POP",                                                   --方差
       VAR_SAMP (sal)
          AS "VAR_SAMP"                                                 --样本方差
  FROM scott.emp
group  by deptno