Question

我在android中第一次使用SQLite并且遇到了这个异常 android.database.sqlite.SQLiteException: no such table: employees (code 1)。我不知道如何解决这个问题。谁能请帮忙。

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener, Activity {

    public static final String DATABASE_NAME = "myemployeedatabase";

    TextView textViewViewEmployees;
    EditText editTextName, editTextSalary;
    Spinner spinnerDepartment;

    SQLiteDatabase mDatabase;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textViewViewEmployees = (TextView) findViewById(R.id.textViewViewEmployees);
        editTextName = (EditText) findViewById(R.id.editTextName);
        editTextSalary = (EditText) findViewById(R.id.editTextSalary);
        spinnerDepartment = (Spinner) findViewById(R.id.spinnerDepartment);

        findViewById(R.id.buttonAddEmployee).setOnClickListener(this);
        textViewViewEmployees.setOnClickListener(this);

        //creating a database
        mDatabase = openOrCreateDatabase(DATABASE_NAME, MODE_PRIVATE, null);
    }
@Override
public void createEmployeeTable() {
        mDatabase.execSQL(
                "CREATE TABLE IF NOT EXISTS employees (\n" +
                        "    id int NOT NULL CONSTRAINT employees_pk PRIMARY KEY,\n" +
                        "    name varchar(200) NOT NULL,\n" +
                        "    department varchar(200) NOT NULL,\n" +
                        "    joiningdate datetime NOT NULL,\n" +
                        "    salary double NOT NULL\n" +
                        ");"
        );
    }
    //this method will validate the name and salary
    //dept does not need validation as it is a spinner and it cannot be empty
    private boolean inputsAreCorrect(String name, String salary) {
        if (name.isEmpty()) {
            editTextName.setError("Please enter a name");
            editTextName.requestFocus();
            return false;
        }

        if (salary.isEmpty() || Integer.parseInt(salary) <= 0) {
            editTextSalary.setError("Please enter salary");
            editTextSalary.requestFocus();
            return false;
        }
        return true;
    }

    //In this method we will do the create operation
    private void addEmployee() {
        String name = editTextName.getText().toString().trim();
        String salary = editTextSalary.getText().toString().trim();
        String dept = spinnerDepartment.getSelectedItem().toString();

        //getting the current time for joining date
        Calendar cal = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        String joiningDate = sdf.format(cal.getTime());

        //validating the inptus
        if (inputsAreCorrect(name, salary)) {

            String insertSQL = "INSERT INTO employees \n" +
                    "(name, department, joiningdate, salary)\n" +
                    "VALUES \n" +
                    "(?, ?, ?, ?);";

            //using the same method execsql for inserting values
            //this time it has two parameters
            //first is the sql string and second is the parameters that is to be binded with the query
            mDatabase.execSQL(insertSQL, new String[]{name, dept, joiningDate, salary});

            Toast.makeText(this, "Employee Added Successfully", Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.buttonAddEmployee:

                addEmployee();

                break;
            case R.id.textViewViewEmployees:

                startActivity(new Intent(this, EmployeeActivity.class));

                break;
        }
    }
}

logcat的

android.database.sqlite.SQLiteException: no such table: employees (code 1): , while compiling: INSERT INTO employees 
                                                                             (name, department, joiningdate, salary)
                                                                             VALUES 
                                                                             (?, ?, ?, ?);
                                                                             #################################################################
                                                                             Error Code : 1 (SQLITE_ERROR)
                                                                             Caused By : SQL(query) error or missing database.
                                                                                (no such table: employees (code 1): , while compiling: INSERT INTO employees 
                                                                             (name, department, joiningdate, salary)
                                                                             VALUES 
                                                                             (?, ?, ?, ?);)

DBHelper

public class DBHelper extends SQLiteOpenHelper {
        // If you change the database schema, you must increment the database version.
        public static final int DATABASE_VERSION = 1;
        public static final String DATABASE_NAME = "myemployeedatabase";

        public DBHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }
        public void onCreate(SQLiteDatabase db) {

            db.execSQL("CREATE TABLE "+ EmployeesEntity.TABLE_NAME+" ("
                    + EmployeesEntity.id+" INTEGER PRIMARY KEY AUTOINCREMENT, "
                    + EmployeesEntity.name  +" TEXT,"
                    + EmployeesEntity.department  +" TEXT,"
                    + EmployeesEntity.joiningdate  +" INTEGER,"
                    + EmployeesEntity.salary  +" REAL);");
        }
        private class EmployeesEntity implements BaseColumns {
            public static final String TABLE_NAME = "employees ";

            public static final String id  = "id";
            public static final String name  = "name";
            public static final String department  = "department";
            public static final String joiningdate   = "joiningdate ";
            public static final String salary   = "salary ";
        }
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            // This database is only a cache for online data, so its upgrade policy is
            // to simply to discard the data and start over

            onCreate(db);
        }
        public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            onUpgrade(db, oldVersion, newVersion);
        }
    }

Answer 1

我认为您的问题是您按照mDatabase = openOrCreateDatabase(DATABASE_NAME, MODE_PRIVATE, null);创建数据库，然后单击TextView，它会触发调用调用onClickListener方法的addEmployee insert SQLiteDatabase createEmployeeTable()方法。在此阶段，由于您尚未创建表，因此数据库为空。

您有两个简单的选项可以解决此问题： -

选项1

第一种是调用//creating a database mDatabase = openOrCreateDatabase(DATABASE_NAME, MODE_PRIVATE, null); createEmployeeTable(); //<<<< ADDED，例如添加行

SQLiteDatabase mDatabase;

选项2

第二种方法是利用你编写的DBHelper。这样做： -

为DBHelper添加一个类变量（比如DBHelper mDBHlpr;之后），例如

    //creating a database
    mDatabase = openOrCreateDatabase(DATABASE_NAME, MODE_PRIVATE, null);

而不是： -
```
//creating a database
mDBHlpr = new DBHelper(this);
mDatabase = mDBHlpr.getWritableDatabase();
```
- 有： -
```
onCreate
```
- 请注意。第二种方法将要求删除数据库（见下文），因为只有在创建数据库时才会调用DBHelper的createEmployeeTable()方法。

我建议第二个选项更可取（然后可以删除{{1}}方法。）

我还建议删除应用数据或卸载应用（删除现有数据库）

注意以上代码是原则上的代码，尚未经过测试，可能包含输入错误。

Answer 2

尝试将compile 'com.facebook.stetho:stetho:1.5.0'放在您的gradle上，这样您就可以在chrome://inspect上看到您的数据库（如果已创建）

另外，尝试通过创建新类来创建数据库和表。

public class DBHelper extends SQLiteOpenHelper {

 // Database Information
public static final String DB_NAME = "DATABASE_NAME";

// database version
static final int DB_VERSION = 1;


 //<editor-fold desc="CREATE_KMPost_TABLE QUERY">
private static final String CREATE_KMPost_TABLE = "CREATE TABLE IF NOT EXISTS " + KM_Post + "("
        + KMPost_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
        + ROUTE_NAME + " VARCHAR,"
        + PLACE + " VARCHAR,"
        + POST + " INTEGER,"
        + PRICE + " DOUBLE,"
        + DISCOUNTED_PRICE + " DOUBLE,"
        + PRICE2 + " DOUBLE,"
        + DISCOUNTED_PRICE2 + " DOUBLE,"
        + PRICE3 + " DOUBLE,"
        + DISCOUNTED_PRICE3 + " DOUBLE)";
//</editor-fold>

 public DBHelper(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(CREATE_KMPost_TABLE);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    onCreate(db);
}

Answer 3

好吧我猜你在创建数据库时遇到的问题

您正在处理SQlite没有MYSQL或SQLSERVER

所以你可以尝试一下

db.execSQL("CREATE TABLE "+ EmployeesEntity.TABLE_NAME+" ("
                + EmployeesEntity.id+" INTEGER PRIMARY KEY AUTOINCREMENT, "
                + EmployeesEntity.name  +" TEXT,"
                + EmployeesEntity.department  +" TEXT,"
                + EmployeesEntity.joiningdate  +" INTEGER,"
                + EmployeesEntity.salary  +" REAL);");

并添加此类

  private class EmployeesEntity implements BaseColumns {
        public static final String TABLE_NAME = "employees ";

        public static final String id  = "id";
        public static final String name  = "name";
        public static final String department  = "department";
        public static final String joiningdate   = "joiningdate ";
        public static final String salary   = "salary ";
    }

现在您可以轻松地进行查询而无需担心名称

<强>更新

你使用datetime作为String ..最好将它用作Long Variable

就像我在SQL strutcre中所做的那样

所以在你的插入查询中不要把DateTime作为字符串你可以在这里获取它

    Calendar calendar = Calendar.getInstance();
    values.put(Time,calendar.getTimeInMillis());

Answer 4

使用SQLiteOpenHelper课来代替您处理工作。它将为您提供所需的必要工作方法。

您可以看到Android培训提供的示例here。

public class FeedReaderDbHelper extends SQLiteOpenHelper {
    // If you change the database schema, you must increment the database version.
    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "FeedReader.db";

    public FeedReaderDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_ENTRIES);
    }
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // This database is only a cache for online data, so its upgrade policy is
        // to simply to discard the data and start over
        db.execSQL(SQL_DELETE_ENTRIES);
        onCreate(db);
    }
    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        onUpgrade(db, oldVersion, newVersion);
    }
}

找不到桌子

4 个答案:

选项1

选项2