這裏寫目錄標題
一、mapper接口中的方法
方法 | 功能說明 |
---|---|
long countByExample(EmployeeExample example) ; | 按條件計數 |
int deleteByExample(EmployeeExample example); | 按條件刪除 |
int deleteByPrimaryKey(Integer id); | 按主鍵刪除 |
int insert(Employee record); | 插入數據 |
int insertSelective(Employee record); | 按條件插入數據 |
List selectByExample(EmployeeExample example); | 按條件查詢 |
Employee selectByPrimaryKey(Integer id); | 按主鍵查詢 |
int updateByExampleSelective(@Param(“record”) Employee record, @Param(“example”) EmployeeExample example); | 按條件更新值不爲null的字段 |
int updateByExample(@Param(“record”) Employee record, @Param(“example”) EmployeeExample example); | 按條件更新 |
int updateByPrimaryKeySelective(Employee record); | 按主鍵更新值不爲null的字段 |
int updateByPrimaryKey(Employee record); | 按主鍵更新 |
二、example實例
mybatis的逆向工程中會生成實例及實例對應的example,example/ XXXExample就是封裝查詢條件,相當於where後面部分
XxxExample.java中包含一個static的內部類Criteria,Criteria就是拼裝查詢條件
xxxExample example = new xxxExample();
Criteria criteria = new Example().createCriteria();
項目 | Value |
---|---|
example.setOrderByClause(“字段名 ASC”) | 添加升序排列條件,DESC爲降序 |
example.setDistinct(false) | 去除重複,boolean型,true爲選擇不重複的記錄 |
criteria.andXxxIsNull | 添加字段xxx爲null的條件 |
criteria.andXxxIsNotNull | 添加字段xxx不爲null的條件 |
criteria.andXxxEqualTo(value) | 添加xxx字段等於value條件 |
criteria.andXxxNotEqualTo(value) | 添加xxx字段不等於value條件 |
criteria.andXxxGreaterThan(value) | 添加xxx字段大於value條件 |
criteria.andXxxGreaterThanOrEqualTo(value) | 添加xxx字段大於等於value條件 |
criteria.andXxxLessThan(value) | 添加xxx字段小於value條件 |
criteria.andXxxLessThanOrEqualTo(value) | 添加xxx字段小於等於value條件 |
criteria.andXxxIn(List<?>) | 添加xxx字段值在List<?>條件 |
criteria.andXxxNotIn(List<?>) | 添加xxx字段值不在List<?>條件 |
criteria.andXxxLike(“%”+value+”%”) | 添加xxx字段值爲value的模糊查詢條件 |
criteria.andXxxNotLike(“%”+value+”%”) | 添加xxx字段值不爲value的模糊查詢條件 |
criteria.andXxxBetween(value1,value2) | 添加xxx字段值在value1和value2之間條件 |
criteria.andXxxNotBetween(value1,value2) | 添加xxx字段值不在value1和value2之間條件 |
三、方法示例
1.統計數量:countByExample
代碼示例:
// exampple相當於where後面的
EmployeeExample example = new EmployeeExample();
EmployeeExample.Criteria criteria = example.createCriteria();
//添加 username 字段 值爲k 的模糊條件查詢
criteria.andUserNameLike("%k%");
long count = mapper.countByExample(example);
相當於SQL語句:
select count(*) from employee WHERE user_name like k;
結果:
2.查詢數據:selectByExample和 selectByPrimaryKey
selectByPrimaryKey:
Employee employee = mapper.selectByPrimaryKey(1);
System.out.println(employee);
相當於SQL:
select * from employee where id = 1;
selectByExample:
//exampple相當於where後面的
EmployeeExample example = new EmployeeExample();
EmployeeExample.Criteria criteria = example.createCriteria();
//添加username 字段 值爲g的模糊查詢
criteria.andUserNameLike("%k%");
// 添加 age字段 大於16的條件
criteria.andAgeGreaterThan(16);
//通過age字段進行排序
example.setOrderByClause("age");
List<Employee> list = mapper.selectByExample(example);
for (Employee employee: list){
System.out.println(employee);
}
相當於SQL:
select *from employee WHERE ( user_name like ? and age > ? ) order by age;
3.插入數據 :insert,insertSelective
Employee employee = new Employee();
employee.setUserName("Mary");
employee.setAge(22);
employee.setEmail("mary.163.com");
employee.setDeptId(1);
mapper.insert(employee);
相當於SQL:
insert into employee (id, user_name, age, email, dept_id) values (null,"Mary“, 22, "mary.163.com", 1)
insertSelective:
Employee employee = new Employee();
employee.setUserName("bob");
employee.setAge(25);
mapper.insertSelective(employee);
相當於SQL:
insert into employee ( user_name, age ) values ( “bob”, 25 )
4.更新數據: updateByExample和updateByExampleSelective,updateByPrimaryKey和updateByPrimaryKeySelective
updateByExample:
//exampple相當於where後面的
EmployeeExample example = new EmployeeExample();
EmployeeExample.Criteria criteria = example.createCriteria();
criteria.andUserNameEqualTo("kong");
Employee employee = new Employee();
employee.setId(3);
employee.setUserName("Linda");
employee.setEmail("Linda.162.com");
employee.setAge(25);
employee.setDeptId(2);
mapper.updateByExample(employee,example);
相當於SQL:
update employee set id = 3, user_name = "Linda", age = 25, email = "Linda.162.com", dept_id = 2 WHERE ( user_name = "kong" )
updateByExampleSelective:
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
//exampple相當於where後面的
EmployeeExample example = new EmployeeExample();
EmployeeExample.Criteria criteria = example.createCriteria();
criteria.andUserNameEqualTo("Jack");
Employee employee = new Employee();
employee.setEmail("jack.162.com");
employee.setAge(30);
mapper.updateByExampleSelective(employee,example);
相當於SQL:
update employee SET age = 30, email = “jack.162.com” WHERE ( user_name = “Jack” )
updateByPrimaryKey:
int updateByPrimaryKey(Employee record);
Employee employee = new Employee();
employee.setId(5);
employee.setUserName("kong");
employee.setAge(16);
employee.setEmail("hk.163.com");
mapper.updateByPrimaryKey(employee);
update employee set user_name = kong, age = 16, email = hk.163.com, dept_id = null where id = 5
updateByPrimaryKeySelective:
int updateByPrimaryKeySelective(Employee record);
Employee employee = new Employee();
employee.setId(6);
employee.setUserName("diligentkong");
mapper.updateByPrimaryKeySelective(employee);
相當於SQL:
update employee SET user_name = diligentkong where id = 6
5.刪除數據:deleteByExample和deleteByPrimaryKey
deleteByExample:
//exampple相當於where後面的
EmployeeExample example = new EmployeeExample();
EmployeeExample.Criteria criteria = example.createCriteria();
//添加 年齡在20-30之間的查詢條件
criteria.andAgeBetween(20,30);
mapper.deleteByExample(example);
相當於SQL:
delete from employee WHERE ( age between 20 and 30 );
deleteByPrimaryKey:
mapper.deleteByPrimaryKey(7);
相當於SQL:
delete from employee where id = ?
參考文章:https://blog.csdn.net/biandous/article/details/65630783