選擇字段爲空的記錄

Question

我需要從表中選擇某些列，其中某列（pos_report_id，在我的情況下）是空的，而不是空。我想在此SQLiteDatabaseBrowser代碼（USER_ID = '23' ），它工作正常：

"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 + "'"; 

，但在代碼中，當我運行應用程序，我得到這個錯誤：

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' 

任何想法如何解決這個問題？爲什麼它不符合''？

Answer 1

user_id是數據庫中的char字段嗎？似乎是一個整數。如果此權利將「'從23中刪除。

Answer 2

在您的查詢中，您同時使用了WHERE和ON子句。嘗試這一個只是一個小的改變，而不是在哪裏使用AND：

"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 + "'";