drupal数据库数据获取与多个具有相同列的表

I am trying to fetch the data from multiple tables "having same column names" but it doesn't give me required results in drupal. here is my code.

$result = db_query ( "select table1.symbol, table2.symbol, table1.price_sales, table2.price_sales from {table1, table2} where table1.uid = table2.uid" );

while ( $obj = $result->fetch () ) {
    echo ($obj->table1.symbol);  // it doesn't return the results
    echo ($obj->table2.symbol);
}

fetch() is not a method to the DatabaseStatementInterface on Dupral 7.x. Try fetchAllAssoc() or fetchAllKeyed()

See the DatabaseStatementInterface Documentation

You should be able to change the name of any column when running the query:

$result = db_query ( "select table1.symbol as second_symbol, table2.symbol, table1.price_sales, table2.price_sales from {table1, table2} where table1.uid = table2.uid" );

while ( $obj = $result->fetch () ) {
    echo ($obj->table1.second_symbol);
    echo ($obj->table2.symbol);
}