JSqlParser - Getting table name from Column

Question

I have just started to explore JSqlparser. According to my understanding, I have modified the TablesNamesFinder to extract columns and tables and its working fine but a very small problem.

@Override
public void visit(Column col) {
    Column c = col;
    String cname = c.getFullyQualifiedName();
    Table t = c.getTable();
    System.out.println(t.getName());
}

This wont print table, for most of the cases it prints null and for very few cases it prints alias of the table but not the table. Is there anything I am forgetting?

Rest of the visits

@Override
public void visit(SelectExpressionItem exp){
    exp.getExpression().accept(this);  
}        

@Override
public void visit(Table tableName) {
   // System.out.println(tableName.getFullyQualifiedName()); 
}

@Override
public void visit(Select select) {
    select.getSelectBody().accept(this);
}

Answer 1

First of all your sourcecode is correct. You have to keep in mind:

JSqlParser is only a parser. So if you do something like

select col1 from table1

The parser generated object Column does not know its tablename. This is only the case if you write it fully qualified:

select table1.col1 from table1

Similar behaviour occurs with aliases. JSqlParser does not expand alias definitions.

Why? If you look at this example, which is a correct SQL:

select col1 from table1, table2

it becomes clear, that calculating the table the column belongs to needs the database schema itself.