sql sever中保证每个班的学生人数不能超过60人
时间: 2023-08-10 21:02:51 浏览: 65
可以通过以下 SQL 语句来实现:
1. 创建一个触发器,使得在插入或更新学生信息时,自动检查该班级的学生人数是否超过了60人:
```
CREATE TRIGGER check_class_size
ON students
AFTER INSERT, UPDATE
AS
BEGIN
IF EXISTS (
SELECT class_id, COUNT(*) AS class_size
FROM students
GROUP BY class_id
HAVING COUNT(*) > 60
)
BEGIN
RAISERROR ('The class size limit of 60 has been exceeded.', 16, 1)
ROLLBACK TRANSACTION
END
END
```
2. 创建一个约束,使得在插入或更新学生信息时,自动检查该班级的学生人数是否超过了60人:
```
ALTER TABLE students
ADD CONSTRAINT check_class_size
CHECK (
NOT EXISTS (
SELECT class_id, COUNT(*) AS class_size
FROM students
GROUP BY class_id
HAVING COUNT(*) > 60
)
)
```
相关问题
请用sqlsever语句帮我查询每系学生人数
Sure, here's the SQL Server statement to help you query the number of students in each department:
SELECT Department, COUNT(*) as StudentCount
FROM Students
GROUP BY Department
请用sqlsever具体语句帮我查询每系学生人数
Sure, here's the SQL query to get the number of students in each department:
SELECT department, COUNT(*) as total_students
FROM students
GROUP BY department;
This will give you a result set with two columns: the name of each department and the total number of students in that department.