COUNT () function
1, COUNT () function is used to count the number of records;
SELECT COUNT(*) FROM t_grade; SELECT COUNT(*) AS total FROM t_grade;
2, used in conjunction with GOUPE BY keyword;
SELECT stuName,COUNT(*) FROM t_grade GROUP BY stuName;
SUN () function
1, SUM () function is a summation function;
SELECT stuName,SUM(score) FROM t_grade WHERE stuName="张三";
2, used in conjunction with GOUPE BY keyword;
SELECT stuName,SUM(score) FROM t_grade GROUP BY stuName;
AVG () function
1, AVG () function is a function of averaging;
SELECT stuName,AVG(score) FROM t_grade WHERE stuName="张三";
2, used in conjunction with GOUPE BY keyword;
SELECT stuName,AVG(score) FROM t_grade GROUP BY stuName;
MAX () function
1, MAX () function is a function of the maximum demand;
SELECT stuName,course,MAX(score) FROM t_grade WHERE stuName="张三";
2, used in conjunction with GOUPE BY keyword;
SELECT stuName,MAX(score) FROM t_grade GROUP BY stuName;
MIN () function
1, MIN () function is a function of selecting the minimum value;
SELECT stuName,course,MIN(score) FROM t_grade WHERE stuName="张三";
2, used in conjunction with GOUPE BY keyword
SELECT stuName,MIN(score) FROM t_grade GROUP BY stuName;