Question

我有一个应用程序，它根据5个文本字段中的信息将信息存储在数据库中。我无法对字段进行排序，甚至只能从一个字段中进行排序。另外，ORDER BY子句采用什么方法？数据库的代码片段如下：

 public static final String MYDATABASE_NAME = "MY_DATABASE";
 public static final String MYDATABASE_TABLE = "MY_TABLE";
 public static final int MYDATABASE_VERSION = 1;
 public static final String KEY_CONTENT = "Content";

 public static final String lastName = "lastName";
 public static final String firstName = "firstName";
 public static final String school = "school";
 public static final String email = "email";
 public static final String intrest = "intrest";




      Cursor d = sqLiteDatabase.rawQuery("SELECT * from " + MYDATABASE_TABLE + "ORDER BY " + lastName + " ASC" , null); 
             while (d.moveToNext()) {
                 int sort = d.getColumnIndex(lastName);
                 int sort2 = d.getColumnIndex(intrest);
                 String lastName = d.getString(sort);
                 String intrest = d.getString(sort2);
                 System.out.println("GOT STUDENT " +  lastName + " LIKES " + intrest);
             }

Answer 1

尝试在代码中使用（cursor.getCount（）＆gt; 0）方法和（cursor！= null）条件来检查是否获取数据。我已经在下面展示了。并尝试使用Log查询完美的查询，并将该查询放入sqlite数据库以检查它是否正常工作。

Cursor d = sqLiteDatabase.rawQuery("SELECT * from " + MYDATABASE_TABLE + " ORDER BY " + lastName + " ASC" , null); // here I have edited space before ORDER BY word starts. Please note this
Log.d("query",">>>>"+SELECT * from " + MYDATABASE_TABLE + " ORDER BY " + lastName + " ASC"); // check this query is going to right way or not using local database.
if(d != null){
     if(d.getCount() > 0){  // to check you get one or more data 
       d.moveToFirst();    
         do{
                 int sort = d.getColumnIndex(lastName);
                 int sort2 = d.getColumnIndex(intrest);
                 String lastName = d.getString(sort);
                 String intrest = d.getString(sort2);
                 System.out.println("GOT STUDENT " +  lastName + " LIKES " + intrest);
           } while (d.moveToNext());
      }
}

试试这个。希望它会对你有所帮助。

Answer 2

我更喜欢查询方法，因为它更清晰：

public static final String MYDATABASE_NAME = "MY_DATABASE";
public static final String MYDATABASE_TABLE = "MY_TABLE";
public static final int MYDATABASE_VERSION = 1;
public static final String KEY_CONTENT = "Content";

public static final String lastName = "lastName";
public static final String firstName = "firstName";
public static final String school = "school";
public static final String email = "email";
public static final String interest = "interest";
public final String[] columns = new String[] {
    lastName,
    firstName,
    school,
    email,
    interest
};

public void printInOrder(String column) {
    Cursor d = sqLiteDatabase.query(MYDATABASE_TABLE, columns, null, null, null, null, column + " ASC");
    while (d.moveToNext()) {
        int sort = d.getColumnIndex(lastName);
        int sort2 = d.getColumnIndex(interest);
        String lastName = d.getString(sort);
        String interest = d.getString(sort2);
        System.out.println("GOT STUDENT " +  lastName + " LIKES " + interest);
    }
}

你如何在SQLite数据库中搜索或排序？

2 个答案: