Hexo

JAP

1. @Entity

2. @Table

3. @Id

4. @Query

5. Sort sort = new Sort(Sort.Direction.DESC, “id”); —→ findAll(sort)

6. Pageable pageable=PageRequest.of(0,5); 第一页 一页5条

7. extends JpaRepository<T, ID>

8. List findByUsername(String username)

   interface PersonRepository extends Repository<User, Long> {
      // and 的查询关系
      List<User> findByEmailAddressAndLastname(EmailAddress emailAddress, String lastname);
      // 包含 distinct 去重，or 的 sql 语法
      List<User> findDistinctPeopleByLastnameOrFirstname(String lastname, String firstname);
      // 根据 lastname 字段查询忽略大小写
      List<User> findByLastnameIgnoreCase(String lastname);
      // 根据 lastname 和 firstname 查询 equal 并且忽略大小写
      List<User> findByLastnameAndFirstnameAllIgnoreCase(String lastname, String firstname); 
     // 对查询结果根据 lastname 排序，正序
      List<User> findByLastnameOrderByFirstnameAsc(String lastname);
     // 对查询结果根据 lastname 排序，倒序
      List<User> findByLastnameOrderByFirstnameDesc(String lastname);
   }


link: Spring Data JPA - Reference Documentation

(16条消息) SpringDataJpa的使用 – 条件查询、排序查询、分页查询_十⑧的博客-CSDN博客_jpa 条件查询

stream

1. list.stream().map(People::getAge)
2. filter(i -> i > 5)
3. count()
4. collect(Collectors.toList()
5. People::getAge

tree

1. code parent_code （queryProcessTree）

   1. 找父节点
   2. 遍历寻找子节点
   3. 递归
   4. 封装数据返回

2. queryLazyProcessTree 懒加载去除孩子节点数据（估计前端点击展开后继续往下查询）

   1. 找父节点
   2. 找所有ChildNode
   3. isleaf = ChildNode.getParentCode.equals(ParentsCode).count==0 ? false : true
   4. 封装返回

3. recursive sql

with recursive temp(id,username,pid,pname) AS (
	SELECT k.id,k.username,k.pid,k.username from t_parent_kid k WHERE k.username='B'
	UNION ALL
	SELECT k.id,k.username,t.id,t.username from temp t,t_parent_kid k WHERE t.id=k.pid
)
SELECT * from temp



union all / union

uniall 整合两张表 上下连接，去重

uniall all 整合两张表 上下连接，列出全部