Android 选择字段为空的记录

我需要从表中选择一些列，其中某一列（在我的例子中是pos_report_id）为空，而不是null。我在SQLiteDatabaseBrowser（针对用户_id='23'）中尝试了这段代码，效果很好：

"SELECT information_action.target_type, information_action.message_type,"
                + "information_action.start_date, information_action.end_date, information_action.content, information_action.status "
                + "FROM information_action INNER JOIN information_to_user ON "
                + "information_to_user.information_action_id = information_action.id_information_action "
                + "WHERE information_action.pos_report_id ='' AND information_to_user.user_id ='"
                + user_id + "'";

但在代码中，当我运行应用程序时，会出现以下错误：

ERROR   AndroidRuntime  Caused by: android.database.sqlite.SQLiteException: near "": syntax error: , while compiling: SELECT information_action.target_type, information_action.message_type,information_action.start_date, information_action.end_date, information_action.content, information_action.status FROM information_action INNER JOIN information_to_user ON information_to_user.information_action_id = information_action.id_information_action WHERE information_action.pos_report_id ='' AND information_to_user.user_id ='23'

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你知道怎么解决这个问题吗？为什么对“”不合适？

用户id是数据库中的字符字段吗？似乎是一个整数。如果此权限从23中删除“”。

在查询中，您同时使用了

WHERE

和

ON

子句。尝试这一项只是一个小小的改变，而不是在何处使用和：

"SELECT information_action.target_type, information_action.message_type,"
                + "information_action.start_date, information_action.end_date, information_action.content, information_action.status "
                + "FROM information_action INNER JOIN information_to_user ON "
                + "information_to_user.information_action_id = information_action.id_information_action "
                + "AND information_action.pos_report_id ='' AND information_to_user.user_id ='"
                + user_id + "'";

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问题不在于用户id，而在于pos报告id。我必须检查pos报告id是否为空。