SELECT * FROM A JOIN B ON B.ID = A.ID AND B.Time = (SELECT max(Time) FROM B B2 WHERE B2.ID = B.ID)
I am trying to join these two tables in MYSQL. Don’t pay attention to that if the ID is unique then I wouldn’t be trying to do this. I condensed the real solution to paint a simplified picture. I am trying to grab and join the table B on the max date for a certain record. This procedure is getting run by an SSIS package and is saying B2.ID is an unknown column. I do things like this frequently in MSSQL and am new to MYSQL. Anyone have any pointers or ideas?
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I do this type of query differently, with an exclusion join instead of a subquery. You want to find the rows of B which have the max Time for a given ID; in other words, where no other row has a greater Time and the same ID.
SELECT A.*, B.* FROM A JOIN B ON B.ID = A.ID LEFT OUTER JOIN B AS B2 ON B.ID = B2.ID AND B.Time < B2.Time WHERE B2.ID IS NULL
You can also use a derived table, which should perform better than using a correlated subquery.
SELECT A.*, B.* FROM A JOIN B ON B.ID = A.ID JOIN (SELECT ID, MAX(Time) AS Time FROM B GROUP BY ID) AS B2 ON (B.ID, B.Time) = (B2.ID, B2.Time)
P.S.: I’ve added the
greatest-n-per-group tag. This type of SQL question comes up every week on Stack Overflow, so you can follow that tag to see dozens of similar questions and their answers.