mp实现条件查询

一、wapper介绍

Wrapper ： 条件构造抽象类，最顶端父类

AbstractWrapper ： 用于查询条件封装，生成 sql 的 where 条件

    QueryWrapper ： Entity 对象封装操作类，不是用lambda语法

    UpdateWrapper ： Update 条件封装，用于Entity对象更新操作

AbstractLambdaWrapper ： Lambda 语法使用 Wrapper统一处理解析 lambda 获取 column。

    LambdaQueryWrapper ：看名称也能明白就是用于Lambda语法使用的查询Wrapper

    LambdaUpdateWrapper ： Lambda 更新封装Wrapper

二、AbstractWrapper

注意：以下条件构造器的方法入参中的 column 均表示数据库字段

1、ge、gt、le、lt、isNull、isNotNull

例如:查询大于80岁的用户

//查询大于80岁的用户
    @Test
    public void testSelectDemo1(){
        //构造条件
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        //age>80
        wrapper.gt("age",80);
        List<User> users = userMapper.selectList(wrapper);
        System.out.println(users);
    }

SQL语句 : SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND age > ?

2、eq、ne

注意：seletOne返回的是一条实体记录，当出现多条时会报错
例如:查询用户名称为jack 并且年龄为20

@Test
    public void testSelectDemo2(){
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        //用户名为jack
        wrapper.eq("name","Tom");
        wrapper.eq("age",28);
        List<User> users = userMapper.selectList(wrapper);
        System.out.println(users);
    }

SQL : SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name = ? AND age = ?

3、between、notBetween

包含大小边界
例如: 查询年龄为20到40的用户

 @Test
    public void testSelectDemo3(){
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        //年龄在20-40
        wrapper.between("age",20,40);
        List<User> users = userMapper.selectList(wrapper);
        System.out.println(users);
    }

SQL ： SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND age BETWEEN ? AND ?

4、allEq

 @Test
    public void testSelectList(){
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        Map<String,Object> map = new HashMap<>();
        map.put("id",2);
        map.put("name","Jack");
        map.put("age",20);
        wrapper.allEq(map);
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }

SQL语句: SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name = ? AND id = ? AND age = ?

5、like、notLike、likeLeft、likeRight

selectMaps返回Map集合列表

 @Test
    public void testSelectMaps(){
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.notLike("name","e")
                .likeRight("email","t");
        List<Map<String, Object>> maps = userMapper.selectMaps(wrapper);
        maps.forEach(System.out::println);
    }

SQL语句: SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name NOT LIKE ? AND email LIKE ?

6、in、notIn、inSql、notinSql、exists、notExists

in、notIn：

• notIn(“age”,{1,2,3})—>age not in (1,2,3)

• notIn(“age”, 1, 2, 3)—>age not in (1,2,3)

inSql、notinSql：可以实现子查询

• 例: inSql(“age”, “1,2,3,4,5,6”)—>age in (1,2,3,4,5,6)
• 例: inSql(“id”, “select id from table where id < 3”)—>id in (select id from table where id < 3)

@Test
    public void testSelectObjs(){
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.inSql("id","select id from user where id < 3");
        List<Object> objects = userMapper.selectObjs(wrapper);
        objects.forEach(System.out::println);
    }

SQL： SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND id IN (select id from user where id < 3)

7、or、and

注意：这里使用的是 UpdateWrapper

不调用or则默认为使用 and 连

@Test
    public void testUpdate1(){
        //修改值
        User user = new User();
        user.setAge(99);
        user.setName("Andy");
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper.like("name","h")
                .or()
                .between("age",20,30);
        int i = userMapper.update(user, userUpdateWrapper);
        System.out.println(i);
    }

SQL语句: UPDATE user SET name=?, age=?, update_time=? WHERE deleted=0 AND name LIKE ? OR age BETWEEN ? AND ?

8、orderBy、orderByDesc、orderByAsc

// A code block
var foo = 'bar';

9、last

直接拼接到 sql 的最后

注意：只能调用一次,多次调用以最后一次为准 有sql注入的风险,请谨慎使用

@Test
    public void testLast(){
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.last("limit 1");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }

SQL语句: SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 limit 1

10、指定要查询的列

 @Test
    public void testSelectDemo4(){
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        //查询指定的列
        wrapper.select("id","name","age");
        wrapper.like("name","a");
        wrapper.orderByDesc("age");
        List<User> users = userMapper.selectList(wrapper);
        System.out.println(users);
    }

SQL语句: SELECT id,name,age FROM user WHERE deleted=0 AND name LIKE ? ORDER BY age DESC

11、set、setSql

最终的sql会合并 user.setAge()，以及 userUpdateWrapper.set() 和 setSql() 中 的字段

@Test
    public void testUpdateSet(){
        //修改值
        User user = new User();
        user.setAge(99);
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper.like("name","h")
                .set("name","李老头")
                .setSql("email='[email protected]");
        int i = userMapper.update(user,userUpdateWrapper);
    }