【引言】
使用mybatis-plus框架的基础上，直接使用其中的条件参数进行查询还是很方便的。但每次使用到像大于、不等于这样一些不常用条件时，都需要现查，所以记录在这篇博客里，当作一个自己的查询手册。
【手册】
| 查询方式 | 说明 |
|---|---|
| select | 设置查询字段 |
| and | AND 语句，拼接 + AND (字段=值) |
| or | 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 |
| 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 |
| last | 拼接在最后，例如：last(“LIMIT 1”) |
【示例】
- select查询指定字段
代码使用：
//查询作者和编码字段，返回Article中其他字段的值均为null
public Article searchOne(Integer id) {LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();queryWrapper.select(Article::getAuthor,Article::getCode).eq(Article::getId,id);return articleMapper.selectOne(queryWrapper);
}
sql打印：
- and和or：并且或者条件
代码使用：
public List<Article> searchMore(String keywords) {LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();queryWrapper.eq(Article::getCatId,10);queryWrapper.and(x->x.like(Article::getKeywords,keywords).or().like(Article::getTitle,keywords));return articleMapper.selectList(queryWrapper);
}
sql打印：
- ge：大于等于条件
代码使用：
//查询条件：访问量大于等于100
public List<Article> searchByCondition() {LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();//大于等于queryWrapper.ge(Article::getVisits,100);//查询指定字段queryWrapper.select(Article::getAuthor,Article::getCode,Article::getTitle,Article::getVisits);return articleMapper.selectList(queryWrapper);
}
sql打印：
- in：批量条件
代码使用：
//栏目Id属于10和20的
public List<Article> searchByCondition() {LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();//inLong[] catId = {10L,20L};List<Long> catList = Arrays.asList(catId);queryWrapper.in(Article::getCatId,catList);//查询指定字段queryWrapper.select(Article::getAuthor,Article::getCode,Article::getTitle,Article::getVisits);return articleMapper.selectList(queryWrapper);
}
sql打印:
- between：范围条件
代码使用：
//查询发布时间在2020-05-01至2020-06-25
public List<Article> searchByCondition() {LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();//betweenqueryWrapper.between(Article::getPublishTime, LocalDate.of(2020,5,1),LocalDate.now().plusMonths(1));//查询指定字段queryWrapper.select(Article::getAuthor,Article::getCode,Article::getTitle,Article::getVisits);return articleMapper.selectList(queryWrapper);
}
sql打印：
- order：排序条件
代码使用：
//查询指定栏目下所有，并按访问量和创建时间排序
public List<Article> searchByCondition() {LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();queryWrapper.eq(Article::getCatId,20);//查询指定字段queryWrapper.select(Article::getAuthor,Article::getCode,Article::getTitle,Article::getVisits);//按访问量和创建时间排序queryWrapper.orderByDesc(Article::getVisits).orderByAsc(Article::getCreateTime);return articleMapper.selectList(queryWrapper);
}
sql打印：
