java 22

SQL语句

• 查询
  select ··
  from ··
  where··
  like··
  between ·· and ··
  as
• 条件查询
  and=“并”集合
  or=“或”集合
  in=“在···范围内”

##根据课程代号（code）查找所有可选的课程设置        
 SELECT 
    co.id 'course_id',
    co.code 'course_code',
    co.name 'course_name',
    co.description 'course_description',
    co.credit 'course_credir',
    ct.id 'course_template_id',
    ct.course_type_id ,
    ct.create_datetime,
    cf.id 'course_offered_id',
    cf.class_capacity,
    cf.class_remain,
    cf.class_time
FROM
    course_template ct,
    course co,
    course_offered cf
WHERE
    cf.course_template_id = ct.id
        AND ct.course_id = co.id
        AND co.code = '数据库'
        and  cf.class_remain >0;

• 插入语句
  Insert into table( ···)
  vlaues（）

insert into student(id,firstname,lastname,phone,email,gender,age,student_status_id,accommodation_id,sid)values(2,'萧','燚','15705799575','[email protected]','男',19,1,2,102);

• 更新语句
  update （table···）
  set ···
  where ···
  禁用安全更新
  set sql_safe_updates =0;
  开启安全更新
  set sql_safe_updates =1;

set sql_safe_updates=0;

UPDATE student 
SET 
    student_status_id = 1
WHERE
    gender = '男'; 

UPDATE teacher t 
SET 
    t.firstname = '栗子',
    t.lastname = '西'
WHERE
    t.id = 4;

set sql_safe_updates=1;

• 排序
  order by （用于对结果排序）··· desc 降序
  order by （用于对结果排序）··· asc 升序

select* from  student order by  age asc;
select* from  student order by  sid desc;