目录

• QueryWrapper排序的坑
• 条件构造器QueryWrapper
• 案例一
• 案例二
• 案例三
• 案例四

QueryWrapper排序的坑

大致可以总结成上面的两句话。

条件构造器QueryWrapper

我们再搞几个实例来深入理解下条件构造器QueryWrapper的用法：

案例一

查询姓李的，并且出生日期范围是1993-02-09到1994-04-09的员工

sql实现：

SELECT * FROM t_employee WHERE DATE_FORMAT(birthday,'%Y-%m-%d')>='1993-02-09' AND DATE_FORMAT(birthday,'%Y-%m-%d')<='1994-04-09' AND NAME LIKE '李%'

mp实现：

/**
 * 查询姓李的，并且出生日期范围是1993-02-09到1994-04-09的员工
 * sql：SELECT * FROM t_employee WHERE DATE_FORMAT(birthday,'%Y-%m-%d')>='1993-02-09' AND DATE_FORMAT(birthday,'%Y-%m-%d')<='1994-04-09' AND NAME LIKE '李%'
 */
@Test
public void selectByQueryWrapper3(){
  QueryWrapper<Employee> queryWrapper=new QueryWrapper();
  // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>query();
  queryWrapper.apply("DATE_FORMAT(birthday,'%Y-%m-%d')>={0} and DATE_FORMAT(birthday,'%Y-%m-%d')<={1}","1993-02-09","1994-04-09").likeRight("name","李");
  List<Employee> employeeList = employeeMapper.selectList(queryWrapper);
  System.out.println(employeeList);
}

案例二

查询姓李的或者邮箱不为空并且是女性的员工

sql实现：

SELECT * FROM t_employee WHERE NAME LIKE '李%' OR (email IS NOT NULL AND gender ='女')

mp实现：

/**
 * 查询姓李的或者邮箱不为空并且是女性的员工
 * sql：SELECT * FROM t_employee WHERE NAME LIKE '李%' OR (email IS NOT NULL AND gender ='女')
 */
@Test
public void selectByQueryWrapper4(){
  QueryWrapper<Employee> queryWrapper=new QueryWrapper();
  // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>query();
  queryWrapper.likeRight("name","李").or(wq->wq.isNotNull("email").eq("gender","女"));
  List<Employee> employeeList = employeeMapper.selectList(queryWrapper);
  System.out.println(employeeList);
}

案例三

查询姓李的并且邮箱不为空或者是女性的员工

sql实现： 

SELECT * FROM t_employee WHERE NAME LIKE '李%' AND (email IS NOT NULL OR gender ='女')

mp实现：

/**
 * 查询姓李的并且邮箱不为空或者是女性的员工
 * sql：SELECT * FROM t_employee WHERE NAME LIKE '李%' AND (email IS NOT NULL OR gender ='女')
 */
@Test
public void selectByQueryWrapper5(){
  QueryWrapper<Employee> queryWrapper=new QueryWrapper();
  // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>query();
  queryWrapper.likeRight("name","李").and(wq->wq.isNotNull("email").or().eq("gender","女"));
  List<Employee> employeeList = employeeMapper.selectList(queryWrapper);
  System.out.println(employeeList);
}

案例四

查询属于编号1,2,3部门的并且薪水小于等于3500的员工 根据年龄从大到小排序显示

sql实现：

SELECT * FROM t_employee WHERE salary<=3500 AND departmentId IN (1,2,3) ORDER BY birthday ASC

mp实现：

/**
 * 查询属于编号1,2,3部门的并且薪水小于等于3500的员工 根据年龄从大到小排序显示
 * sql：SELECT * FROM t_employee WHERE salary<=3500 AND departmentId IN (1,2,3) ORDER BY birthday ASC
 */
@Test
public void selectByQueryWrapper6(){
  QueryWrapper<Employee> queryWrapper=new QueryWrapper();
  // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>query();
  queryWrapper.likeRight("name","李").and(wq->wq.isNotNull("email").or().eq("gender","女"));
  List<Employee> employeeList = employeeMapper.selectList(queryWrapper);
  System.out.println(employeeList);
}

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。