在2个日期之间的日期联接2个表

Question

I am trying to find a location of a customer on a given date and time in one table and update another table. I have to generate letters (PDFs) with the right address at the time of the letter. The customer has a movement record in a table that tells where he was on a given date and time. For example, we generate a letter to customer AAA with a date of 05/03/2016. It should have an address location of LocA. Customer BBB gets a letter with a date 05/22/2016 and it should have a location of LocE. I need to update CustomerLetter.AddressLocation with the value from CustomerMovement.AddressLocation , and I can't seem to get started on this.

Here are my tables.

CREATE global temporary TABLE CustomerLetter (CustomerID varchar2(6), AddressLocation varchar2(6), LetterDate date);
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('AAA', NULL, '2016-05-03');
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('AAA', NULL, '2016-05-05');
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('AAA', NULL, '2016-08-14');
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('BBB', NULL, '2016-05-02');
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('BBB', NULL, '2016-05-29');
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('BBB', NULL, '2016-07-22');
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('CCC', NULL, '2016-03-06');
INSERT INTO CustomerLetter (CustomerID, AddressLocation, LetterDate) VALUES ('CCC', NULL, '2016-11-25');
commit;
CREATE global temporary TABLE CustomerMovement (CustomerID varchar2(6), ActionDate date, AddressLocation varchar2(6));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('AAA', 'locA', TO_DATE('2016-05-02 09:05:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('AAA', 'locA', TO_DATE('2016-05-04 14:05:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('AAA', 'locB', TO_DATE('2016-05-04 22:00:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('AAA', 'locE', TO_DATE('2016-07-02 20:00:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('AAA', 'locA', TO_DATE('2016-06-03 06:10:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('BBB', 'locE', TO_DATE('2016-05-10 03:00:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('BBB', 'locF', TO_DATE('2016-06-01 03:00:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('CCC', 'locA', TO_DATE('2016-10-10 03:00:00', 'yyyy-mm-dd HH24:MI:SS'));
INSERT INTO CustomerMovement (CustomerID, AddressLocation, ActionDate) VALUES ('CCC', 'locA', TO_DATE('2016-12-03 03:00:00', 'yyyy-mm-dd HH24:MI:SS'));
commit;

Answer 1

Use a subquery in your UPDATE statement to query the appropriate addressLocation value for each letter.

Using the tables and data you posted in your question, that would be something like this:

update CustomerLetter cl
SET addresslocation = ( SELECT cm.addressLocation  
                        FROM   CutomerMovement cm
                        WHERE  cm.customerID = cl.customerID
                        AND    cm.actionDate <= cl.letterDate
                        ORDER BY cm.actionDate DESC
                        FETCH FIRST 1 ROW ONLY );

For each letter, find the customer movements that happened prior to the letterDate . Then, use the addressLocation from most recent of those movements.

If a letter has no customer movement records prior to the letter date, the address location for that letter will be null .