如何使用where子句在sqlite中检索数据？

时间：2018-06-02 17:44:03

标签： sqlite android-sqlite

我已将CSV文件中的数据导入SQLite表。 当我尝试使用特定列检索记录时，它返回0条记录。然而，数据存在 在表中。 表格的架构：

public static final class Vehicle2Wheel implements BaseColumns{
    public static final String TABLE_NAME="Vehicle2Wheel";
    public static final String VEH_ID = "VEH_ID";
    public static final String VEH_REG_NUM = "VEH_REG_NUM";
    public static final String VEH_ENGINE_NO = "VEH_ENGINE_NO";
    public static final String VEH_CHASIS_NO= "VEH_CHASIS_NO";
    public static final String VEH_MAKE= "VEH_MAKE";
    public static final String VEH_CC = "VEH_CC";
    public static final String VEH_COLOR = "VEH_COLOR";
    public static final String VEH_MODEL = "VEH_MODEL";
    public static final String OWN_NAME = "OWN_NAME";
    public static final String OWN_FNAME = "OWN_FNAME";
    public static final String CNIC = "OWN_CNIC";
    public static final String OWN_ADDRESS = "OWN_ADDRESS";
}

创建表：

String tableVeh2Wheel = "CREATE TABLE "+ Schema.Vehicle2Wheel.TABLE_NAME+
            " ("+ Schema.Vehicle2Wheel.VEH_ID+" TEXT,"
            + Schema.Vehicle2Wheel.VEH_REG_NUM+" TEXT,"
            + Schema.Vehicle2Wheel.VEH_ENGINE_NO+" TEXT,"
            + Schema.Vehicle2Wheel.VEH_CHASIS_NO+" TEXT,"
            + Schema.Vehicle2Wheel.VEH_MAKE+" TEXT,"
            + Schema.Vehicle2Wheel.VEH_CC+" TEXT,"
            + Schema.Vehicle2Wheel.VEH_COLOR+" TEXT,"
            + Schema.Vehicle2Wheel.VEH_MODEL+ " TEXT,"
            + Schema.Vehicle2Wheel.OWN_NAME+" TEXT,"
            + Schema.Vehicle2Wheel.OWN_FNAME+" TEXT,"
            + Schema.Vehicle2Wheel.CNIC+" TEXT,"
            + Schema.Vehicle2Wheel.OWN_ADDRESS+" TEXT"
            + ");";

从CSV文件导入数据的代码：

public void setData(String filePath, String tableName, int colCount, String[] colNames){
    SQLiteDatabase db = getWritableDatabase();
    db.execSQL("delete from " + tableName);

    try {
        FileReader file = new FileReader(filePath);

        BufferedReader buffer = new BufferedReader(file);
        ContentValues contentValues = new ContentValues();
        String line = "";
        db.beginTransaction();

        while ((line = buffer.readLine()) != null) {

            String[] str = line.split(",",colCount);

            int length = str.length;

            for (int i = 0; i < length; i++) {
                contentValues.put(colNames[i], str[i].toString());
            }


            db.insert(tableName, null, contentValues);

        }
        db.setTransactionSuccessful();
        db.endTransaction();
    } catch (IOException e) {
        if (db.inTransaction())
            db.endTransaction();

        Toast.makeText(context,""+e.getMessage().toString(), Toast.LENGTH_SHORT).show();
    }
    if (db.inTransaction())
        db.endTransaction();
}

此代码（代码1）返回游标计数零： 代码1： 

database = new Database(getApplicationContext());
    SQLiteDatabase db = database.getWritableDatabase();

        Cursor cursor = null;
        String vehId = "";
        try {
            String value = "KIL-3396";
            cursor = db.rawQuery("SELECT VEH_ID FROM Vehicle2Wheel WHERE VEH_REG_NUM=?", new String[] {value + ""});
            if(cursor.getCount() > 0) {
                cursor.moveToFirst();
                vehId = cursor.getString(cursor.getColumnIndex("VEH_ID"));
                Log.v(TAG,"Vehicle ID is "+vehId);
            }else
                Log.v(TAG,"no record, size of cursor is "+cursor.getCount());

        }finally {
            cursor.close();

        }

此代码的输出显示在图片p1 picture p1

中

然而，此（下面）代码返回注册号“KIL-3396”。这表示该记录存在于表中， 但为什么不使用代码检索（即代码1）。为什么注册号“KIL-3396”不匹配？ 除VEH_ID外，不使用任何列检索数据。

String query = "SELECT * FROM Vehicle2Wheel LIMIT 5;";
    Cursor mcursor = db.rawQuery(query, null);
    if (mcursor.getCount()>0) {
        mcursor.moveToFirst();
        while (mcursor.moveToNext()) {
            for (int i = 0; i < mcursor.getColumnCount(); i++) {
                Log.v(TAG, "Data is " + mcursor.getString(i));

            }
        }
    }

此代码的输出显示在图片p2 picture p2

中

1 个答案:

答案 0 :(得分：0)

我强烈怀疑如果您将第二个代码更改为： - 

String query = "SELECT * FROM Vehicle2Wheel LIMIT 5;";
Cursor mcursor = db.rawQuery(query, null);
if (mcursor.getCount()>0) {
    mcursor.moveToFirst();
    while (mcursor.moveToNext()) {
        for (int i = 0; i < mcursor.getColumnCount(); i++) {
            Log.v(TAG, "Data is " + mcursor.getString(i));

        }
    }
}

Cursor cursor = null;
String vehId = "";
try {
    String value = "KIL-3396";
    cursor = db.rawQuery("SELECT VEH_ID FROM Vehicle2Wheel WHERE VEH_REG_NUM=?", new String[] {value + ""});
    if(cursor.getCount() > 0) {
        cursor.moveToFirst();
        vehId = cursor.getString(cursor.getColumnIndex("VEH_ID"));
        Log.v(TAG,"Vehicle ID is "+vehId);
    } else
        Log.v(TAG,"no record, size of cursor is "+cursor.getCount());

    }finally {
        cursor.close();

    }

您将获得预期的结果。即代码1的位置/位置/顺序是问题，并且从提供的代码中无法确定具体问题。

我测试你的代码： - 

06-02 22:21:00.399 1672-1672/va.vehicleapp V/SEARCHACTIVITY: Vehicle ID is 3
    Data is 3
    Data is KIL-3396
    Data is 12345678
    Data is 12345678
    Data is Suzuki
    Data is 125
    Data is Red
    Data is GL
    Data is FrederickSon
    Data is Fred
    Data is 12345678
    Data is 1 The Fred, Fredickstown
  • 在测试中我已经编制了数据，但REG编号除外（2行，注意moveToFirst跳过第一行，只显示1行）

以下代码用于测试： - 

private void lookAtRecords(SQLiteDatabase db) {
    String TAG = "SEARCHACTIVITY";


    Cursor cursor = null;
    String vehId = "";
    try {
        String value = "KIL-3396";
        cursor = db.rawQuery("SELECT VEH_ID FROM Vehicle2Wheel WHERE VEH_REG_NUM=?", new String[] {value + ""});
        if(cursor.getCount() > 0) {
            cursor.moveToFirst();
            vehId = cursor.getString(cursor.getColumnIndex("VEH_ID"));
            Log.v(TAG,"Vehicle ID is "+vehId);
        }else
            Log.v(TAG,"no record, size of cursor is "+cursor.getCount());

    }finally {
        if (cursor != null) {
            cursor.close();
        }

    }

    String query = "SELECT * FROM Vehicle2Wheel LIMIT 5;";
    Cursor mcursor = db.rawQuery(query, null);
    if (mcursor.getCount()>0) {
        mcursor.moveToFirst();
        while (mcursor.moveToNext()) {
            for (int i = 0; i < mcursor.getColumnCount(); i++) {
                Log.v(TAG, "Data is " + mcursor.getString(i));

            }
        }
    }
}
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