Left join with complex join clause - sql

Question

I have two tables and want to left join them.
I want all entries from the account table, but only rows matching a criteria from the right table. If no criteria is matching, I only want the account.
The following does not work as expected:
SELECT * FROM Account a
LEFT JOIN
Entries ef ON ef.account_id = a.account_id AND
(ef.entry_period_end_date BETWEEN $periodStartDate_escaped AND LAST_DAY(date_add( $periodStartDate_escaped, INTERVAL $periodLengthInMonths_escaped MONTH))
OR
ef.forecast_period_end BETWEEN $periodStartDate_escaped AND LAST_DAY(date_add( $periodStartDate_escaped, INTERVAL $periodLengthInMonths_escaped MONTH))
OR
ef.entry_period_end_date IS NULL
OR
ef.forecast_period_end IS NULL
)
cause it also gives me the rows from the entries table, which are outside the requested period.
Example Data:
Account Table
AccountID | AccountName
1 Test
2 Foobar
3 Test1
4 Foobar2
Entries Table
id | AccountID | entry_period_end_date | forecast_period_end | amount
1 1 12/31/2009 12/31/2009 100
2 1 NULL 10/31/2009 150
3 2 NULL NULL 200
4 3 10/31/2009 NULL 250
5 4 10/31/2009 10/31/2009 300
So the query should return (when i set startDate = 12/01/2009, endDate 12/31/2009)
AccountID | id
1 1
2 NULL
3 NULL
4 NULL
Thx,
Martin

Answer 1

If either entry_period_end_date or forecast_period_end is NULL, the row will be returned, even if your other, non-NULL column is not within the period.
Probably you meant this:
SELECT *
FROM Account a
LEFT JOIN
Entries ef
ON ef.account_id = a.account_id
AND
(
entry_period_end_date BETWEEN …
OR forecast_period_end BETWEEN …
)
, which will return you all rows with either entry_period_end or forecast_period_end within the given period.
Update:
A test script:
CREATE TABLE account (AccountID INT NOT NULL, AccountName VARCHAR(100) NOT NULL);
INSERT
INTO account
VALUES
(1, 'Test'),
(2, 'Foobar'),
(3, 'Test1'),
(4, 'Foobar1');
CREATE TABLE Entries (id INT NOT NULL, AccountID INT NOT NULL, entry_period_end_date DATETIME, forecast_period_end DATETIME, amount FLOAT NOT NULL);
INSERT
INTO Entries
VALUES
(1, 1, '2009-12-31', '2009-12-31', 100),
(2, 1, NULL, '2009-10-31', 100),
(3, 2, NULL, NULL, 100),
(4, 3, '2009-10-31', NULL, 100),
(5, 4, '2009-10-31', '2009-10-31', 100);
SELECT a.*, ef.id
FROM Account a
LEFT JOIN
Entries ef
ON ef.accountID = a.accountID
AND
(
entry_period_end_date BETWEEN '2009-12-01' AND '2009-12-31'
OR forecast_period_end BETWEEN '2009-12-01' AND '2009-12-31'
);
returns following:
1, 'Test', 1
2, 'Foobar', NULL
3, 'Test1', NULL
4, 'Foobar1' NULL

Answer 2

Edited to fix logic so end date logic is grouped together, then forecast period logic...
Now it should check for a "good" end date (null or within range), then check for a "good" forecast date (null or within range)
Since all the logic is on the Entries table, narrow it down first, then join
SELECT a.*,temp.id FROM Account a
LEFT JOIN
(
SELECT id, account_id
FROM Entries ef
WHERE
((ef.entry_period_end_date BETWEEN $periodStartDate_escaped AND LAST_DAY(date_add( $periodStartDate_escaped, INTERVAL $periodLengthInMonths_escaped MONTH))
OR
ef.entry_period_end_date IS NULL
)
AND
(ef.forecast_period_end BETWEEN $periodStartDate_escaped AND LAST_DAY(date_add( $periodStartDate_escaped, INTERVAL $periodLengthInMonths_escaped MONTH))
OR
ef.forecast_period_end IS NULL
)
) temp
ON a.account_id = temp.account_id