Question

我很难弄清楚为什么在向表中插入值时会出现错误。谢谢你的帮助。

基本上，该代码仅在只有两列和一个contentValues.put函数时才起作用，但是，当我添加另一列时，尝试插入值时总是出错，我也不知道为什么。

我已经检查了SQlite查询等。

package com.avrahamzilberblat.battleshipfinal;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String TAG = "DatabaseHelper";
    private static final String TABLE_NAME = "people_table";
    private static final String COL1 = "ID";
    private static final String COL2 = "name";
    private static final String COL3 = "scoreRatio";

    public DatabaseHelper(Context context) {

        super(context, TABLE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        //String createTable = "CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +COL2 +" TEXT,"+ COL3 +"INTEGER"+");";
        db.execSQL("CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COL2 +" TEXT,"+COL3+"TEXT)");



    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {
        db.execSQL("DROP IF TABLE EXISTS " + TABLE_NAME);
        onCreate(db);
    }

    public boolean addData(String item,int scoreRatio) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL2, item);
        contentValues.put(COL3, 5);


        long result = db.insert(TABLE_NAME, null, contentValues);

        //if date as inserted incorrectly it will return -1
        if (result == -1) {
            return false;
        } else {
            return true;
        }
    }

    /**
     * Returns all the data from database
     * @return
     */
    public Cursor getData(){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "SELECT * FROM " + TABLE_NAME;
        Cursor data = db.rawQuery(query, null);
        return data;
    }

    /**
     * Returns only the ID that matches the name passed in
     * @param name
     * @return
     */
    public Cursor getItemID(String name,Double scoreRatio){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "SELECT " + COL1 + " FROM " + TABLE_NAME +
                " WHERE " + COL2 + " = '" + name + "'" + " AND " +COL3 + " = '" + scoreRatio+"'";
        Cursor data = db.rawQuery(query, null);
        return data;
    }

    /**
     * Updates the name field
     * @param newName
     * @param id
     * @param oldName
     */
    public void updateName(String newName, int id, String oldName){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "UPDATE " + TABLE_NAME + " SET " + COL2 +
                " = '" + newName + "' WHERE " + COL1 + " = '" + id + "'" +
                " AND " + COL2 + " = '" + oldName + "'";
        Log.d(TAG, "updateName: query: " + query);
        Log.d(TAG, "updateName: Setting name to " + newName);
        db.execSQL(query);
    }

    /**
     * Delete from database
     * @param id
     * @param name
     */
    public void deleteName(int id, String name){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "DELETE FROM " + TABLE_NAME + " WHERE "
                + COL1 + " = '" + id + "'" +
                " AND " + COL2 + " = '" + name + "'";
        Log.d(TAG, "deleteName: query: " + query);
        Log.d(TAG, "deleteName: Deleting " + name + " from database.");
        db.execSQL(query);
    }
    public void clearDatabase(String TABLE_NAME) {
        SQLiteDatabase db = this.getWritableDatabase();
        String clearDBQuery = "DELETE FROM "+TABLE_NAME;
        db.execSQL(clearDBQuery);
    }

}

--------------------这是我想要一个字符串和双精度数据类型的更新，仍然无法正常工作

@Override
public void onCreate(SQLiteDatabase db) {
    //String createTable = "CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +COL2 +" TEXT,"+ COL3 +"INTEGER"+");";
    db.execSQL("CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
            COL2 +" TEXT,"+COL3 +"REAL);");



}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {
    db.execSQL("DROP IF TABLE EXISTS " + TABLE_NAME);
    onCreate(db);
}

public boolean addData(String item,int scoreRatio) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COL2, "ood");
    contentValues.put(COL3, 6.6);

Answer 1

您应该更改：-

db.execSQL("CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
            COL2 +" TEXT,"+COL3+"TEXT)");

至：-

db.execSQL("CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY, " +
            COL2 +" TEXT,"+COL3+" TEXT)");

然后您应该执行以下一项操作：-

从设置/应用中删除（清除）应用的数据。
卸载应用程序。
增加数据库版本，例如将super(context, TABLE_NAME, null, 1);更改为super(context, TABLE_NAME, null, 2);

，然后重新运行该应用程序。

上面的内容很重要，因为 onCreate 在创建数据库时只会自动运行一次，这可能是问题的根本原因。您已添加一列，但实际上尚未添加。

我玩过很多次，我实际上希望它是一个实数例如Double，所以一开始我写的是REAL，而不是TEXT

SQlite允许将任何类型的数据存储在任何类型的列中，只有一个例外，那就是rowid的别名（使用INTEGER PRIMARY KEY定义的列（带或不带AUTOINCREMENT））。 rowid的别名只能存储一个整数（带符号的64位），并且在表中必须是UNIQUE。

注意AUTOINCREMENT已被省略。您很可能不需要它，并且有开销

SQLite Autoincrement

其中包括：-

AUTOINCREMENT关键字强加了额外的CPU，内存，磁盘空间和磁盘I / O开销，如果没有严格要求，则应避免。它是通常不需要。

无法将值插入SQLite表

1 个答案: