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DROP TABLE students;
CREATE TABLE students(stuId INT PRIMARY KEY,stuName VARCHAR(20),stuAge INT); DESC students;
INSERT INTO students VALUES(1,'张三',18); INSERT INTO students VALUES(1,'李四',20); SELECT * FROM students;
DROP TABLE students; CREATE TABLE students(stuId INT,stuName VARCHAR(20),stuAge INT DEFAULT 18);
INSERT INTO students VALUES(1,'张三',17); INSERT INTO students VALUES(2,'李四',NULL); INSERT INTO students(stuId,stuName) VALUES(3,'王五'); SELECT * FROM students;
DROP TABLE students; CREATE TABLE students(stuId INT,stuName VARCHAR(20) NOT NULL,stuAge INT DEFAULT 18);
INSERT INTO students VALUES(1,NULL,17);
DROP TABLE dept; CREATE TABLE dept(id INT,deptName VARCHAR(20) UNIQUE);
INSERT INTO dept VALUES (1,'工程部'); INSERT INTO dept VALUES (2,'销售部'); INSERT INTO dept VALUES (3,'工程部'); SELECT * FROM dept;
DROP TABLE students; CREATE TABLE students(sid INT PRIMARY KEY AUTO_INCREMENT,stuName VARCHAR(20),stuAge INT); INSERT INTO students(stuName,stuAge) VALUES('张三',17); INSERT INTO students(stuName,stuAge) VALUES('李四',NULL); INSERT INTO students(stuName,stuAge) VALUES('王五',17); INSERT INTO students(stuName,stuAge) VALUES('赵六',19); SELECT * FROM students;
DELETE FROM students WHERE sid = 3;
DELETE FROM students; TRUNCATE TABLE students;
DESC students;
DROP TABLE dept; CREATE TABLE dept(id INT PRIMARY KEY,departName VARCHAR(20)); INSERT INTO dept VALUES(1,'工程部'); INSERT INTO dept VALUES(2,'销售部'); INSERT INTO dept VALUES(3,'客服部');
DROP TABLE employee; CREATE TABLE employee( id INT, empName VARCHAR(20), deptId INT, CONSTRAINT employee_dept_fk FOREIGN KEY(deptId) REFERENCES dept(id) ON UPDATE CASCADE ON DELETE CASCADE );
DELETE FROM employee;
INSERT INTO employee VALUES(1,'张三',1); INSERT INTO employee VALUES(2,'李四',1); INSERT INTO employee VALUES(3,'王五',1); INSERT INTO employee VALUES(4,'乔布斯',3); INSERT INTO employee VALUES(5,'比尔盖茨',2); INSERT INTO employee VALUES(6,'克林顿',2); INSERT INTO employee VALUES(7,'小布什',4);
SELECT * FROM employee;
UPDATE employee SET deptId = 5 WHERE id = 7;
UPDATE dept SET id = 5 WHERE id = 3; DELETE FROM dept WHERE id = 1;
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