Question

I’d like to know if having to conditionals when using a JOIN keyword is a good practice.

I’m trying to filter this resultset by date but I’m unable to get all the branches listed even if there’s no expense or income for a date using a WHERE clause. Is there a better way of doing this, if so how?

SELECT
  Branches.Name
  ,SUM(Expenses.Amount) AS Expenses
  ,SUM(Incomes.Amount) AS Incomes
FROM
  Branches
  LEFT JOIN Expenses
    ON Branches.Id = Expenses.BranchId AND Expenses.Date = '3/11/2010'
  LEFT JOIN Incomes
    ON Branches.Id = Incomes.BranchId AND Incomes.Date = '3/11/2010'
GROUP BY Branches.Name

Answer 1

Why not? Even more!
OUTER JOIN has very specific trick about these two conditions!
INNER JOIN is tolerant to recombination, for example following are equivalent:

INNER JOIN Expenses
    ON Branches.Id = Expenses.BranchId
WHERE
    Expenses.Date = '3/11/2010'

via:

INNER JOIN Expenses
    ON Branches.Id = Expenses.BranchId AND Expenses.Date = '3/11/2010'

BUT!!! For OUTER JOIN you MUST specify exactly two conditions inside ON, since WHERE would treat result as INNER JOIN