Retrieve default value for IN query condition
Suppose a query retrieves user information and the number of minutes they were online within a specified date range. It uses an IN query to filter users based on their ID. The goal is to return a default value for those IDs that don't have any matching records.
Simplified query:
SELECT users.Name, users.ID, SUM(users.Minutes) AS MinutesOnline FROM UserTable LEFT JOIN OnlineUseage ON OnlineUseage.ID = UserTable.ID WHERE OnlineUseage.Date >= '2016-01-01 00:00:00' AND OnlineUseage.Date < '2016-01-31 00:00:00' AND users.ID IN (1,2,3,4,5);
Modified query:
To achieve the desired results, move the condition for OnlineUseage to the FROM clause. This ensures that the left join behaves like an inner join, filtering out users without any matching records in OnlineUseage.
SELECT users.Name, users.ID, IFNULL(SUM(users.Minutes), 0) AS MinutesOnline FROM users LEFT JOIN OnlineUseage ON OnlineUseage.ID = users.ID AND OnlineUseage.Date >= '2016-01-01 00:00:00' AND OnlineUseage.Date < '2016-01-31 00:00:00' WHERE users.ID IN (1,2,3,4,5);
The query will now retrieve users with matching records in OnlineUseage and users without matching records, while setting MinutesOnline to the default value of 0 for those users without matching records.
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