REGR_AVGY
regr_avgy(y, x) actually calculates the average of y (mathematical expectation), x has no role here.
REGR_SXX
The return value is equal to REGR_COUNT(expr1, expr2) * VAR_POP(expr2) .
REGR_SYY
The return value is equal to REGR_COUNT(expr1, expr2) * VAR_POP(expr1) .
REGR_SXY
The return value is equal to REGR_COUNT(expr1, expr2) * COVAR_POP(expr1, expr2) .
STDDEV
Calculates the standard deviation of the current row about the group.
Example:
Example returns the cumulative standard deviation of salary values for department 30 sorted by date of hire.
select ename,hiredate,sal,stddev(sal) over(order by hiredate) a from emp where deptno=20;
ENAME | HIREDATE | SAL | A
-------+---------------------+------+-------------------
SMITH | 1980-12-17 00:00:00 | 4800 | 1414.213562373095
SMITH | 1980-12-17 00:00:00 | 6800 | 1414.213562373095
JONES | 1981-04-02 00:00:00 | 7975 | 1605.264775667865
FORD | 1981-12-03 00:00:00 | 8000 | 1503.935808692202
SCOTT | 1987-04-19 00:00:00 | 8000 | 1393.24262065155
ADAMS | 1987-05-23 00:00:00 | 8100 | 1309.428946780491
(6 rows)
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