Question

Possible Duplicate:
Is it better to do an equi join in the from clause or where clause

I’m a noob in SQL,i have 2 queries:

SELECT 
    A.COLUMN1,B.COLUMN2, C.COLUMN3
FROM
     TB_ITEM A,
     TB_ITEM_CAT B,
     TB_ITEM_SUBCAT C
WHERE
     A.COLUMN1 = B.COLUMN1
     AND A.COLUMN1 = c.COLUMN1

and

SELECT 
    A.COLUMN1,B.COLUMN2, C.COLUMN3
FROM
     TB_ITEM A 
INNER JOIN TB_ITEM_CAT B on A.COLUMN1 = B.COLUMN1
INNER JOIN TB_ITEM_SUBCAT C on A.COLUMN1 = C.COLUMN1

In first query,we dont have INNER JOINS,and select from 3 tables.
In the second,we have the same query with INNER JOINS,and select from 3 tables.

They are supposed to show same result?
What the difference beetween these queries?

Answer 1

They are semantically the same. A decent optimizer will recognize this an generate equally efficient plans. An experienced SQL coder will also recognize this 😉

Joe Celko quote, “There are at least seven ways to write a query; only two are worth
using.”