java - Android SQLite 不喜欢语法

Question

我想从数据库中选择与已存在的名称不匹配的名称。使用此代码，抛出错误:No such table

public String getRandomAnswer(String correctName){
     String randomAnswer;
     mDbHelper.initializeDataBase();
     try {
         mDb = mDbHelper.getWritableDatabase();
         String sql = "SELECT Name FROM Cities WHERE Name NOT LIKE " + correctName + " ORDER BY Random() LIMIT 1 ";
         Cursor c = mDb.rawQuery(sql, null);
         if (c != null) {
             if (c.moveToFirst()) {
                 randomAnswer = c.getString(c.getColumnIndex("Name"));
                 return randomAnswer;
             }
             c.close();
         }
     } catch (Exception ex) {
         ex.printStackTrace();
     } finally {
         try {
             mDbHelper.close();
         } catch (Exception ex) {
             ex.printStackTrace();
         } finally {
             mDb.close();
         }
     }
     return null;
 }

但是如果我直接输入单词String sql = "SELECT Name FROM Cities WHERE Name NOT LIKE 'someOtherName' ORDER BY Random() LIMIT 1 ";比它有效，但它不是我想要的。

Answer 1

考虑 SQL 参数化而不是字符串连接，因为您需要将变量括在单引号中。否则，引擎假定您引用列或表标识符。方法rawQuery支持参数。此外，不带通配符的 LIKE 应使用相等性 =。但如果需要通配符，请附加到参数。

// PREPARED STATEMENT WITH QMARKS, ?
String sql = "SELECT Name FROM Cities WHERE Name NOT LIKE ? ORDER BY Random() LIMIT 1 ";

// QUERY EXECUTION WITH BINDED VALUE AND WILDCARDS
Cursor c = mDb.rawQuery(sql, new String[]{ "%"+correctName+"%" });