Helo all

I am not really experienced in Structured Query Language, but it seemed strange to me when I came across a piece of code where a query requested data from 3 different tables, but it didn't use the Join clause.

For example, it was like:

select fiel1, field2, field3 from table1, table2 where table1.field1 = table2.field2

As you can see it moved the JOIN logic to the WHERE clause. Is this an accepted way of dealing with multiple tables selection? Doesn't it have any drawbacks?

Thanks in advance

Nick

This syntax is the "old" form of specifying an INNER JOIN. There is nothing inherently wrong with using it, although the SQL-92 standard now suggests the [INNER] JOIN ... ON syntax as preferable, deprecating the old style.

This is perhaps a matter of taste, but I find the "new" style preferable, as it doesn't "clutter" up the WHERE clause with JOIN logic, thus reserving the WHERE clause for row selection, which is its true purpose.

Note that specifying OUTER JOINS with the *= (or =*) infix style in the WHERE clause is a different story. There, true ambiguities can arise depending upon the order of evaluation of various WHERE clause predicates. For OUTER JOINs, use the [LEFT|RIGHT] [OUTER} JOIN ... ON syntax to insure these don't occur.



Jeff Mason
Custom Apps, Inc.
www.custom-apps.com