//查詢name不為空的用戶，并且郵箱不為空的用戶，年齡大于等于12
 @Test
 void selectBy01(){
 ?
     QueryWrapper<User> wrapper=new QueryWrapper<>();
     wrapper
             .isNotNull("name") //name不為空的用戶
             .isNotNull("email") //郵箱不為空的用戶
             .ge("age",12); //年齡大于等于12
 ?
     userMapper.selectList(wrapper).forEach(System.out::println);
 }

//查詢name為 "Jone" 的用戶
 @Test
 void selectBy02(){
 ?
     QueryWrapper<User> wrapper=new QueryWrapper<>();
     wrapper.eq("name","Jone"); //name為 "Jone" 的用戶
 ?
     //查詢一個(gè)數(shù)據(jù)，為多個(gè)用 selectList 或者 selectByMap
     User user = userMapper.selectOne(wrapper);
 ?
     System.out.println(user);
 }

//查詢 10 到 20 歲的用戶數(shù)
 @Test
 void selectBy03(){
     QueryWrapper<User> wrapper=new QueryWrapper<>();
     wrapper.between("age",10,20);
 ?
     Integer count = userMapper.selectCount(wrapper);
     //查詢 10 到 20 歲的用戶的結(jié)果數(shù)
 ?
     System.out.println(count);
 }

@Test
 void selectLike01(){
     QueryWrapper<User> wrapper=new QueryWrapper<>();
     wrapper
             .notLike("name","To") //名字不包含 To
             .like("name","o") //名字包含 o 的
             //左和右 左：%e   右：e%  兩邊：%e%
             //右查詢
             .likeRight("email","test");
 ?
     List<Map<String, Object>> users = userMapper.selectMaps(wrapper);
     users.forEach(System.out::println);
 }

@Test
 void selectLike02(){
     QueryWrapper<User> wrapper=new QueryWrapper<>();
     wrapper
             //一個(gè)SQL語句寫的子查詢
             .inSql("id","select id from user where age<20");
 ?
     List<Object> users = userMapper.selectObjs(wrapper);
     users.forEach(System.out::println);
 }

@Test
 void selectLike03(){
     QueryWrapper<User> wrapper=new QueryWrapper<>();
     //降序排序
     wrapper.orderByDesc("id");
     //升序排序
     //wrapper.orderByAsc("id");
 ?
     List<User> users = userMapper.selectList(wrapper);
     users.forEach(System.out::println);
 }