假设在mysql数据库中,有学生,成绩,老师,课程四张表,表结构如下
学生表,student(s_id,s_name,s_age,s_sex)
教师表,teacher(t_id,t_name)
课程表,course(c_id,c_name,t_id)
成绩表,score(sc_id,s_id,c_id,score)
以下sql正确的是
SELECT student.s_id,s_name FROM student LEFT JOIN score on score.s_id = student.s_id where score.score>60
DELETE FROM teacher WHERE t_name LIKE '陈%'
ALTER TABLE teacher ADD COLUMN s_phone VARCHAR(15) NOT NULL DEFAULT '' COMMENT '联系电话';
ALTER TABLE teacher ADD INDEX sid_index ON s_id;
D: ALTER TABLE table_name ADD column_name datatype 正确写法:alter table teacher add sid long;