使用 Wrapper 查询

# ge gt le lt isNull isNotNull

@Test
public void testWrapperQuery1(){
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper
        .ge("age",22)
        .isNotNull("email");
    List<User> users = userMapper.selectList(queryWrapper);
    System.out.println(users);
}

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同理支持 gt le lt isNull

# eq ne

@Test
public void testWrapperQuery2(){
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.eq("email","work_stt@163.com");
    User user = userMapper.selectOne(queryWrapper);
    System.out.println(user);
}

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注意：selectOne只查询一条记录，如果数据库中匹配到多条记录则会报错

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 2

# between notBetween

注意：包含大小边界

@Test
public void testWrapperQuery3() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.between("age", 18, 20);
    Integer count = userMapper.selectCount(queryWrapper);
    System.out.println(count);
}

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# like notLike likeLeft likeRight

selectMaps() 返回的Map集合列表，通常配合select()使用

@Test
public void testWrapperQuery4() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper
        .select("name", "age")
        .like("name", "st") // like '%st%'
        .likeRight("email", "work_"); // like 'work_%'
    List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);
    maps.forEach(System.out::println);
}

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# orderBy orderByDesc orderByAsc

@Test
public void testWrapperQuery5(){
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.orderByDesc("age","id");
    List<User> users = userMapper.selectList(queryWrapper);
    System.out.println(users);
}

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# 支持的查询方式

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”)

Last Updated: 2022/01/16, 11:29:51

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