基于mybatis-plus QueryWrapper 排序的坑

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。