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 ： 查询条件封装

​ UpdateWrapper ： Update 条件封装

AbstractLambdaWrapper ： 使用Lambda 语法

​ LambdaQueryWrapper ：用于Lambda语法使用的查询Wrapper

​ LambdaUpdateWrapper ： Lambda 更新封装Wrapper

@SpringBootTest
public class QueryWrapperTests {
    
    @Autowired
    private UserMapper userMapper;
}

二、测试用例

1、ge、gt、le、lt、isNull、isNotNull

@Test
public void testDelete() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper
        .isNull("name")
        .ge("age", 12)
        .isNotNull("email");
    int result = userMapper.delete(queryWrapper);
    System.out.println("delete return count = " + result);
}



 @Test
    public void testSelectOne() {
        LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper
                .isNull(User::getName)
                .ge(User::getAge, 12)
                .isNotNull(User::getEmail);
        int result = userMapper.delete(queryWrapper);
        System.out.println("delete return count = " + result);
    }

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

@Test
public void testSelectOne() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.eq("name", "Tom");
    User user = userMapper.selectOne(queryWrapper);//只能返回一条记录，多余一条则抛出异常
    System.out.println(user);
}


    @Test
    public void testSelectOne() {
        LambdaQueryWrapper<User> userLambdaQueryWrapper = new LambdaQueryWrapper<>();
        userLambdaQueryWrapper.eq(User::getName, "Tom");
        User user = userMapper.selectOne(userLambdaQueryWrapper);//只能返回一条记录，多余一条则抛出异常
        System.out.println(user);
    }

3、between、notBetween

包含大小边界

@Test
public void testSelectCount() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.between("age", 20, 30);
    Long count = userMapper.selectCount(queryWrapper); //返回数据数量
    System.out.println(count);
}


    @Test
    public void testSelectCount() {
        LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.between(User::getAge, 20, 30);
        Long count = userMapper.selectCount(queryWrapper);//返回数据数量
        System.out.println(count);
    }

SELECT COUNT( * ) FROM t_user WHERE deleted=0 AND (age BETWEEN ? AND ?)

4、like、notLike、likeLeft、likeRight

selectMaps()返回Map集合列表，通常配合select()使用

@Test
public void testSelectMaps() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper
        .select("name", "age")
        .like("name", "e")
        .likeRight("email", "5");
    List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);//返回值是Map列表
    maps.forEach(System.out::println);
}

5、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> queryWrapper = new QueryWrapper<>();
//        queryWrapper.in("id", 1, 2, 3);
        queryWrapper.inSql("id", "select id from user where id <= 3");
        List<Object> objects = userMapper.selectObjs(queryWrapper);//返回值是Object列表
        objects.forEach(System.out::println);
    }

6、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 result = userMapper.update(user, userUpdateWrapper);
    System.out.println(result);
}

7、lambda表达式

lambda表达式内的逻辑优先运算

@Test
public void testUpdate2() {
    //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", "n")
        .or(i -> i.like("name", "a").eq("age", 20));
    int result = userMapper.update(user, userUpdateWrapper);
    System.out.println(result);
}

8、orderBy、orderByDesc、orderByAsc

@Test
public void testSelectListOrderBy() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.orderByDesc("age", "id");
    List<User> users = userMapper.selectList(queryWrapper);
    users.forEach(System.out::println);
}

9、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(60);
    //修改条件
    UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
    userUpdateWrapper
        .like("name", "h")
        .set("name", "Peter")//除了可以查询还可以使用set设置修改的字段
        .setSql(" email = '943697678@qq.com'");//可以有子查询
    int result = userMapper.update(user, userUpdateWrapper);
}

三、查询方式

查询方式	说明
setSqlSelect	设置 SELECT 查询字段
where	WHERE 语句，拼接 + WHERE 条件
and	AND 语句，拼接 + AND 字段=值
andNew	AND 语句，拼接 + AND (字段=值)
or	OR 语句，拼接 + OR 字段=值
orNew	OR 语句，拼接 + OR (字段=值)
eq	等于=
allEq	基于 map 内容等于=
ne	不等于<>
gt	大于>
ge	大于等于>=
lt	小于<
le	小于等于<=
like	模糊查询 LIKE
notLike	模糊查询 NOT LIKE
in	IN 查询
notIn	NOT IN 查询
isNull	NULL 值查询
isNotNull	IS NOT NULL
groupBy	分组 GROUP BY
having	HAVING 关键词
orderBy	排序 ORDER BY
orderAsc	ASC 排序 ORDER BY
orderDesc	DESC 排序 ORDER BY
exists	EXISTS 条件语句
notExists	NOT EXISTS 条件语句
between	BETWEEN 条件语句
notBetween	NOT BETWEEN 条件语句
addFilter	自由拼接 SQL
last	拼接在最后，例如：last(“LIMIT 1”)