java - 表未删除

Question

我正在尝试删除一个表，我点击了此链接 http://www.techonthenet.com/sqlite/truncate.php作为教程。但是当我执行下面的代码时，第一次运行时，我期望 sqliteFactory.getRowCount()方法将 return 0行作为方法 sqliteFactory.deleteTable(SysConsts.SQLITE_DATABASE_TABLE_NAME);在它之前刚刚被调用，但我收到的是 rowCount它不为零。

在第二次运行相同的代码时，我期望 sqliteFactory.CreateTable(SysConsts.SQLITE_DATABASE_TABLE_NAME);显示Log.i(TAG, "CreateTable", "table: ["+tableName+"] does not exist, will be created");因为该表应该已被删除，但我收到 Log.i(TAG, "CreateTable", "table: ["+tableName+"] already exists.");

请告诉我为什么该表没有被删除？我应该做什么commit删除后？

主要代码:

public static void main(String[] args) throws SQLException, ClassNotFoundException {
    SQLiteFactory sqliteFactory = new SQLiteFactory();
    sqliteFactory.newSQLiteConn(SysConsts.SQLITE_DATABASE_NAME);
    sqliteFactory.CreateTable(SysConsts.SQLITE_DATABASE_TABLE_NAME);

    sqliteFactory.insertRecord(new Record("001", "55.07435", "8.79047", "c:\\bremen_0.xml"));
    Log.d(TAG, "main", "rowCount: "+sqliteFactory.getRowCount());

    //sqliteFactory.selectAll();
    //sqliteFactory.getNodeID("53.074415", "8.788047");
    sqliteFactory.selectXMLPathFor("53.074415", "8.788047");
    Log.d(TAG, "", ""+sqliteFactory.getRowCountLatLngFor("53.074415", "8.788047"));
    Log.d(TAG, "", ""+sqliteFactory.getRowCountNodeIDFor("001"));
    Log.d(TAG, "", ""+sqliteFactory.getRowCountXMLPathFor("c:\\brem_0.xml"));

    sqliteFactory.deleteTable(SysConsts.SQLITE_DATABASE_TABLE_NAME);
    Log.d(TAG, "main", "rowCount: "+sqliteFactory.getRowCount());
}

创建表:

public void CreateTable(String tableName) throws SQLException, ClassNotFoundException {
    if (!this.isTableExists(tableName)) {
        Log.i(TAG, "CreateTable", "table: ["+tableName+"] does not exist, will be created");

        Connection conn = this.getConnection();
        Statement stmt = conn.createStatement();
        stmt.executeUpdate(this.sqlTable);

        stmt.close();
        conn.close();

    } else {
        Log.i(TAG, "CreateTable", "table: ["+tableName+"] already exists.");
        return;
    }
}

isTableExists:

private boolean isTableExists(String tableName) throws ClassNotFoundException, SQLException {
    Connection conn = this.getConnection();
    DatabaseMetaData dbMeta = conn.getMetaData();
    ResultSet resSet = dbMeta.getTables(null, null, tableName, null);
    boolean exists = false;

    if (resSet.next()) {
        exists = true;
    } else {
        exists = false;
    }

    resSet.close();
    conn.close();

    return exists;
}

删除表:

public void deleteTable(String tableName) throws ClassNotFoundException, SQLException {
    if (this.isTableExists(tableName)) {
        Log.i(TAG, "deleteTable", "table: ["+tableName+"] already exists, and will be deleted.");

        Connection conn = this.getConnection();
        PreparedStatement ps = conn.prepareStatement("delete from "+this.TABLE_NAME);

        ps.close();
        conn.close();

    } else {
        Log.i(TAG, "deleteTable", "table: ["+tableName+"] does not exist, can't be deleted.");
        return;
    }
}

获取行计数:

public int getRowCount() throws SQLException, ClassNotFoundException {  
    Connection conn = this.getConnection();
    Statement stmt= conn.createStatement();
    ResultSet resSet = stmt.executeQuery("SELECT COUNT(*) AS rowCount FROM "+TABLE_NAME+";");

    int cnt = resSet.getInt("rowCount");

    resSet.close();
    stmt.close();
    conn.close();

    return cnt;
}

Answer 1

准备语句并不运行它。调用 execute() 来运行 PreparedStatement。