使用oracle来计算方差及标准差

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/* 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)
          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