例说SQLServer2008聚合函数

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 CREATE TABLE tb_Class( classid int NOT NULL IDENTITY, classname NVARCHAR(16) NOT NULL, students int NOT NULL, teacher NVARCHAR(16) NOT NULL, PRIMARY KEY(classid)) INSERT INTO tb_Class(classname,students,

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CREATE TABLE tb_Class(

classid int NOT NULL IDENTITY,

classname NVARCHAR(16) NOT NULL,

students int NOT NULL,

teacher NVARCHAR(16) NOT NULL,

PRIMARY KEY(classid))

INSERT INTO tb_Class(classname,students,teacher)

VALUES

('1班',25,'yl'),('2班',18,'wsp'),('3班',24,'yl'),('4班',25,'zhy'),

('5班',22,'wsp'),('6班',25,'yl'),('7班',20,'zhy'), ('8班',22,'wsp')

SELECT SUM(students) FROM tb_Class GROUP BY teacher

SELECT COUNT(students) FROM tb_Class GROUP BY teacher

SELECT AVG(students) FROM tb_Class GROUP BY teacher

SELECT MAX(students) FROM tb_Class GROUP BY teacher

SELECT MIN(students) FROM tb_Class GROUP BY teacher

，