```java
DbUtils db = DbUtils.create(this);
User user = new User(); //这里需要注意的是User对象必须有id属性,或者有通过@ID注解的属性
user.setEmail("wyouflf@qq.com");
user.setName("wyouflf");
db.save(user); // 使用saveBindingId保存实体时会为实体的id赋值
...
// 查找
Parent entity = db.findById(Parent.class, parent.getId());
Parent entity = db.findFirst(entity);//通过entity的属性查找
List<Parent> list = db.findAll(entity);//通过entity的属性查找
List<Parent> list = db.findAll(Parent.class);//通过类型查找
// IS NULL
Parent Parent = db.findFirst(Selector.from(Parent.class).where("name","=", null));
// IS NOT NULL
Parent Parent = db.findFirst(Selector.from(Parent.class).where("name","!=", null));
// WHERE id<54 AND (age>20 OR age<30) ORDER BY id LIMIT pageSize OFFSET pageOffset
List<Parent> list = db.findAll(Selector.from(Parent.class)
.where("id" ,"<", 54)
.and(WhereBuilder.b("age", ">", 20).or("age", " < ", 30))
.orderBy("id")
.limit(pageSize)
.offset(pageSize * pageIndex));
// op为"in"时,最后一个参数必须是数组或Iterable的实现类(例如List等)
Parent test = db.findFirst(Selector.from(Parent.class).where("id", "in", new int[]{1, 2, 3}));
// op为"between"时,最后一个参数必须是数组或Iterable的实现类(例如List等)
Parent test = db.findFirst(Selector.from(Parent.class).where("id", "between", new String[]{"1", "5"}));