SQLite COUNT
SQLite COUNT函数用于获取表达式的总数。
语法:
SELECT COUNT(aggregate_expression)
FROM tables
[WHERE conditions];
将MAX函数与GROUP BY子句一起使用时的语法:
SELECT expression1, expression2, ... expression_n
COUNT(aggregate_expression)
FROM tables
[WHERE conditions]
GROUP BY expression1, expression2, ... expression_n;
示例1:
我们有一个名为" STUDENT"的表,其中包含以下数据:
计算AGE大于22的" STUDENT"表中的所有学生人数。
SELECT COUNT(*) AS "Number of students"
FROM STUDENT
WHERE AGE > 22;
输出:
示例2:
将GROUP BY子句与COUNT函数一起使用:
对年龄大于22岁的具有特定姓名的学生人数进行计数,并按学生的名字。
SELECT NAME, COUNT(*) AS "Number Of Students"
FROM STUDENT
WHERE AGE > 22
GROUP BY NAME;
输出: