1.LambdaQueryWrapper 的条件构造器方法对应Sql
代码示例：
LambdaQueryWrapper<Employee> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(Employee::getUsername,employee.getUsername());
Employee emp = employeeService.getOne(queryWrapper);
方法：
| setSqlSelect | SELECT 查询字段 |
|---|---|
| where | WHERE 语句，拼接 + WHERE 条件 |
| 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 | NOT LIKE模糊查询 |
| 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”) |
例如：
LambdaQueryWrapper<Notice> lqw = new LambdaQueryWrapper<>();
lqw.eq(Notice::getInviteeId, notice.getInviteeId());
lqw.eq(Notice::getNoticeType, NoticeDO.NOTICE_TYPE);
lqw.orderByDesc(Notice::getCreateTime);
lqw.last("limit 1");select * from notice where invitee_id=179 order by create_time desc limit 1;2.注解的使用
@NotEmpty,@NotNull和@NotBlank的区别
1 @NotEmpty :不能为null，且Size>0
2 @NotNull:不能为null，但可以为empty,没有Size的约束
3 @NotBlank:只用于String,不能为null且trim()之后size>0
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