条件构造器

深碍√TFBOYSˉ_ 2023-10-11 19:51 28阅读 0赞

**目录**

命名DAO对象

编辑

组装查询条件

组装查询包含条件

组装排序条件

组装删除条件

条件的优先级

实现子查询

--------------------

####  ####

#### 命名DAO对象 ####

#### ![0caac88f2d5f403ea1a2baf7f0c444f2.png][] ####

#### 组装查询条件 ####

![ed6dc95cf76749678b3538c0377added.png][]

**代码如下**

@RequestMapping("/test02")
        public List<User> Test02(){
           //创建条件构造器对象
           QueryWrapper<User> userQueryWrapper = new QueryWrapper<User>();
           //select * from t_user where user_name='admin'
           userQueryWrapper.eq("user_name","admin");
           //select * from t_user where user_name='admin' and money between  1300 and 1500
           userQueryWrapper.between("money",1300,1500);
           List<User> list = dao.selectList(userQueryWrapper);
           return list;
       }

### 组装查询包含条件 ###

![f06f33d0b0b942629ab18d90ae823b0b.png][]

@RequestMapping("/test03")
        public List<User> Test03(){
           //查询用户名包含a，年龄在20到30之间，并且邮箱不为null的用户信息
           QueryWrapper<User> userQueryWrapper = new QueryWrapper<User>();
           userQueryWrapper.like("user_name","a").between("money",500,800).isNotNull("id");
           List<User> list = dao.selectList(userQueryWrapper);
           return list;
       }

### 组装排序条件 ###

![212d3542ca6546d590888d1831bb7f40.png][]

@RequestMapping("/test04")
        public List<User> Test04(){
           //按money升序asc排列,如果money相同就按id排列
           QueryWrapper<User> userQueryWrapper = new QueryWrapper<User>();
           userQueryWrapper.orderByAsc("money").orderByDesc("id");
           List<User> list = dao.selectList(userQueryWrapper);
           return list;
       }

### 组装删除条件 ###

![473dc7353fbb425cbbe2063ab91feebb.png][]

@RequestMapping("/test05")
        public int  Tsst05(){
           // //删除money为空的用户 
           QueryWrapper<User> userQueryWrapper = new QueryWrapper<User>();
            userQueryWrapper.isNull("money");
           int count = dao.delete(userQueryWrapper);
           return count;
       }

### 条件的优先级 ###

![a86006a7691542e684b306848f06ee0f.png][]

@RequestMapping("/test07")
        public List<User> Test07(){
           //将money大于1000并且用户名是admin的
           QueryWrapper<User> userQueryWrapper = new QueryWrapper<>();
           userQueryWrapper.like("user_name","admin").gt("money",1000);
           List<User> list = dao.selectList(userQueryWrapper);
           return list;
    
       }

### 实现子查询 ###

![d4c31fddc76f439d81692bea002f458b.png][]

@RequestMapping("/test06")
        public List<User> Test06(){
           QueryWrapper<User> userQueryWrapper = new QueryWrapper<>();
           userQueryWrapper.inSql("id","select id from t_user where id<=3");
           List<User> list = dao.selectList(userQueryWrapper);
           return list;
       }

[0caac88f2d5f403ea1a2baf7f0c444f2.png]: https://img-blog.csdnimg.cn/0caac88f2d5f403ea1a2baf7f0c444f2.png
[ed6dc95cf76749678b3538c0377added.png]: https://img-blog.csdnimg.cn/ed6dc95cf76749678b3538c0377added.png
[f06f33d0b0b942629ab18d90ae823b0b.png]: https://img-blog.csdnimg.cn/f06f33d0b0b942629ab18d90ae823b0b.png
[212d3542ca6546d590888d1831bb7f40.png]: https://img-blog.csdnimg.cn/212d3542ca6546d590888d1831bb7f40.png
[473dc7353fbb425cbbe2063ab91feebb.png]: https://img-blog.csdnimg.cn/473dc7353fbb425cbbe2063ab91feebb.png
[a86006a7691542e684b306848f06ee0f.png]: https://img-blog.csdnimg.cn/a86006a7691542e684b306848f06ee0f.png
[d4c31fddc76f439d81692bea002f458b.png]: https://img-blog.csdnimg.cn/d4c31fddc76f439d81692bea002f458b.png