SQLite AVG()
函数用于检索表达式或给定列的平均值。
语法
SELECT AVG(aggregate_expression)
FROM tables
[WHERE conditions];
在GROUP BY
子句中使用AVG()
函数时的语法:
SELECT expression1, expression2, ... expression_n
AVG(aggregate_expression)
FROM tables
[WHERE conditions]
GROUP BY expression1, expression2, ... expression_n;
示例1:
假设有一个名为student
的表,具有以下数据:
从student
表中检索学生的平均费用(fees
):
SELECT AVG(FEES) AS "Avg Fees"
FROM STUDENT
WHERE ID > 0;
执行上面查询代码,得到以下结果 -
sqlite> SELECT AVG(FEES) AS "Avg Fees"
...> FROM STUDENT
...> WHERE ID > 0;
18777.7777777778
sqlite>
示例2:
使用带有DISTINCT
子句的AVG()
函数,从student
表中获取FEES
大于10000
并且平均不同费用。
SELECT AVG(DISTINCT FEES) AS "Avg Fees"
FROM STUDENT
WHERE FEES > 10000;
执行上面查询代码,得到以下结果 -
sqlite> SELECT AVG(DISTINCT FEES) AS "Avg Fees"
...> FROM STUDENT
...> WHERE FEES > 10000;
28600.0
sqlite>
示例3:
使用数学公式在AVG()
函数中计算求平均值。
可以使用数学公式根据您的要求检索平均值,如下求每个月的平均值 -
SELECT AVG(FEES / 12) AS "Average Monthly Fees"
FROM STUDENT;
执行上面查询代码,得到以下结果 -
sqlite> SELECT AVG(FEES / 12) AS "Average Monthly Fees"
...> FROM STUDENT;
1564.81481481481
sqlite>
示例4:
使用具有的GROUP BY
子句的AVG()
函数:
从student
表中检索NAME
和FEES
,并按AGE
分组数据:
SELECT NAME, SUM(FEES) AS "Avg Fees by Name"
FROM STUDENT
GROUP BY AGE;
执行上面代码,得到以下结果 -
sqlite> SELECT NAME, SUM(FEES) AS "Avg Fees by Name"
...> FROM STUDENT
...> GROUP BY AGE;
Javasu|18000.0
Maxsu|16000.0
Linsu|80000.0
Sqlsu|25000.0
Linsu|30000.0
sqlite>