Cursor cursor = db.query("suser", null, "suno=?", new String[]{"username"};

这是一个使用 Android SQLite 数据库进行查询的代码示例。其中：

- `db` 是一个 `SQLiteDatabase` 对象，表示要查询的数据库。
- `"suser"` 是要查询的表名。
- `null` 表示要返回所有列。
- `"suno=?"` 是查询的条件，其中 `suno` 是列名，`?` 是占位符，表示这个位置要传入查询条件的值。
- `new String[]{"username"}` 是传入的查询条件值，这里是一个字符串数组，表示要查询 `suno` 列等于 `"username"` 的记录。

这个查询语句会返回符合条件的记录。具体返回的数据格式和内容取决于表结构和查询条件。

相关问题

Cursor cursor3= db.rawQuery("SELECT suser.suno , suser.sph,sus.st FROM suser INNER JOIN sus on suser.suno=sus.suno ",new String[]{});

这是一段使用 SQLite 数据库查询语言（SQL）的代码。它从两个表中选择数据并将其连接起来。"suser"和"sus"是两个表的名称。"suser.suno"、"suser.sph"和"sus.st"是所需的列。"INNER JOIN"是一种连接类型，它连接两个表中具有相同值的行。"ON suser.suno=sus.suno"指定了连接条件，即两个表中"suno"列的值相等。最后，"db.rawQuery"函数执行此查询并返回一个游标对象，该对象可用于遍历结果集。

springboot+MyBatis连接MySql数据库遇到问题：### Error querying database. Cause: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure The last packet successfully received from the server was 11,751 milliseconds ago. The last packet sent successfully to the server was 11,858 milliseconds ago. ### The error may exist in file [/app/tomcat/webapps/project/WEB-INF/classes/mapper/PersonWeekMapper.xml] ### The error may involve com.xmsme.mapper.PersonWeekMapper.selectPersonWeekList-Inline ### The error occurred while setting parameters ### SQL: SELECT count(0) FROM (SELECT WEEK.id, WEEK.sub_time, WEEK.need_thing, WEEK.plan_content, WEEK.target_content, WEEK.sub_time AS update_time, WEEK.create_time, WEEK.week_start, WEEK.user_id, WEEK.week_end, readInfo.id AS readId, readInfo.read_status AS readStatus, updateor.nick_name FROM t_person_weekly AS WEEK LEFT JOIN sys_user sUser ON sUser.user_id = WEEK.user_id LEFT JOIN t_read_info readInfo ON readInfo.business_id = WEEK.id AND readInfo.read_type = 'PER' LEFT JOIN sys_user updateor ON updateor.user_id = WEEK.update_by LEFT JOIN sys_user_role uRole ON uRole.user_id = WEEK.update_by LEFT JOIN sys_user_post uPost ON uPost.user_id = WEEK.user_id LEFT JOIN t_project_person person ON person.user_id = WEEK.user_id LEFT JOIN t_project_person Pperson ON Pperson.project_id = person.project_id WHERE 1 = 1 AND WEEK.is_del = 0 AND WEEK.draft = 'N' AND Pperson.user_id = ? GROUP BY WEEK.id) table_count ### Cause: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure The last packet successfully received from the server was 11,751 milliseconds ago. The last packet sent successfully to the server was 11,858 milliseconds ago. ; Communications link failure The last packet successfully received from the server was 11,751 milliseconds ago. The last packet sent successfully to the server was 11,858 milliseconds ago.; nested exception is com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure The last packet successfully received from the server was 11,751 milliseconds ago. The last packet sent successfully to the server was 11,858 milliseconds ago.

这个错误通常是因为与数据库的连接出现了问题。有几个可能的原因导致这个问题：

1. 数据库连接配置错误：请确保你的数据库连接配置正确，包括数据库地址、端口号、用户名和密码等。
2. 数据库服务未启动：请确保你的数据库服务已经启动，并且可以正常访问。
3. 数据库连接超时：如果你的数据库连接超时时间设置得过短，可能会导致连接失败。你可以尝试增加连接超时时间。
4. 网络问题：如果你的网络连接存在问题，可能会导致与数据库的通信失败。请确保你的网络连接正常。

你可以根据以上几点进行排查，看看是否能够解决这个问题。如果还有其他疑问，请提供更多的详细信息，我会尽力帮助你解决。