Differences b / w that condition JOIN clause versus WHERE clause

Question

Suppose I have 3 tables.

Sales Representative

• Rep Code
• Name
• Surname
• Phone
• Email
• Sales department

Orders

• Order number
• Rep Code
• Client's number
• order date
• Order status

Customer

• Client's number
• Name
• The address
• Phone number

I want to receive a detailed sales report for 2010. I would join. I am interested to know which of the following functions is more efficient and why?

SELECT 
    O.OrderNum, R.Name, C.Name
FROM
    Order O INNER JOIN Rep R ON O.RepCode = R.RepCode
            INNER JOIN Customer C ON O.CustomerNumber = C.CustomerNumber
WHERE
    O.OrderDate >= '01/01/2010'

OR

SELECT 
    O.OrderNum, R.Name, C.Name
FROM
    Order O INNER JOIN Rep R ON (O.RepCode = R.RepCode AND O.OrderDate >= '01/01/2010')
            INNER JOIN Customer C ON O.CustomerNumber = C.CustomerNumber

Answer 1

EVENTS should reflect the relationship aspect of your tables. The WHERE clause is where you filter records. I prefer the first one.

Make it readable first, relationships between tables should be obvious (using JOIN), then profile

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