VAR_POP
语法：
VAR_POP([DISTINCT] expr)
功能：分组求数据集的总体方差，作为聚集函数或分析函数。
说明：VAR_POP是计算丢弃空值后的一组确定数值的总体方差。
示例：
返回staffS表中工资的总体方差。
--删除表staffS。
DROP TABLE IF EXISTS staffS;
--创建表staffS。
CREATE TABLE staffS
(
staff_ID NUMBER(6) not null,
FIRST_NAME VARCHAR2(20),
LAST_NAME VARCHAR2(25),
EMAIL VARCHAR2(25),
PHONE_NUMBER VARCHAR2(20),
HIRE_DATE DATE,
employment_ID VARCHAR2(10),
SALARY NUMBER(8,2),
COMMISSION_PCT NUMBER(2,2),
MANAGER_ID NUMBER(6),
section_ID NUMBER(4)
);
--新增数据。
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (198, 'Donald', 'OConnell', 'DOCONNEL', '650.507.9833', to_date('21-06-1999', 'dd-mm-yyyy'), 'SH_CLERK', 2600.00, null, 124, 50);
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (199, 'Douglas', 'Grant', 'DGRANT', '650.507.9844', to_date('13-01-2000', 'dd-mm-yyyy'), 'SH_CLERK', 2600.00, null, 124, 50);
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (200, 'Jennifer', 'Whalen', 'JWHALEN', '515.123.4444', to_date('17-09-1987', 'dd-mm-yyyy'), 'AD_ASST', 4400.00, null, 101, 10);
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (198, 'Donald', 'OConnell', 'DOCONNEL', '650.507.9833', to_date('21-06-1999', 'dd-mm-yyyy'), 'SH_CLERK', 2600.00, null, 124, 50);
--查询工资的总体方差。
SELECT VAR_POP(SALARY) FROM staffs;
VAR_POP(SALARY)
----------------------------------------
607500
1 rows fetched.
VAR_SAMP
语法：
VAR_SAMP([DISTINCT] expr)
功能：分组求数据集的样本方差，作为聚集函数或分析函数。
说明：VAR_SAMP是计算丢弃空值后的一组确定数值的样本方差。
示例：
返回staffS表中工资的样本方差。
--删除表staffS。
DROP TABLE IF EXISTS staffS;
--创建表staffS。
CREATE TABLE staffS
(
staff_ID NUMBER(6) not null,
FIRST_NAME VARCHAR2(20),
LAST_NAME VARCHAR2(25),
EMAIL VARCHAR2(25),
PHONE_NUMBER VARCHAR2(20),
HIRE_DATE DATE,
employment_ID VARCHAR2(10),
SALARY NUMBER(8,2),
COMMISSION_PCT NUMBER(2,2),
MANAGER_ID NUMBER(6),
section_ID NUMBER(4)
);
--新增数据。
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (198, 'Donald', 'OConnell', 'DOCONNEL', '650.507.9833', to_date('21-06-1999', 'dd-mm-yyyy'), 'SH_CLERK', 2600.00, null, 124, 50);
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (199, 'Douglas', 'Grant', 'DGRANT', '650.507.9844', to_date('13-01-2000', 'dd-mm-yyyy'), 'SH_CLERK', 2600.00, null, 124, 50);
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (200, 'Jennifer', 'Whalen', 'JWHALEN', '515.123.4444', to_date('17-09-1987', 'dd-mm-yyyy'), 'AD_ASST', 4400.00, null, 101, 10);
INSERT INTO staffs (staff_ID, FIRST_NAME, LAST_NAME, EMAIL, PHONE_NUMBER, HIRE_DATE, employment_ID, SALARY, COMMISSION_PCT, MANAGER_ID, section_ID)
VALUES (198, 'Donald', 'OConnell', 'DOCONNEL', '650.507.9833', to_date('21-06-1999', 'dd-mm-yyyy'), 'SH_CLERK', 2600.00, null, 124, 50);
--查询工资的样本方差。
SELECT VAR_SAMP(SALARY) FROM staffs;
VAR_SAMP(SALARY)
----------------------------------------
810000
1 rows fetched.
