Select values which changed between two time stamps

Michi :

Table SQL Fiddle:

CREATE TABLE Sales_Planning (
    Time_Stamp DATE,
    Campaign VARCHAR(255),
    Expected_Sales VARCHAR(255)
);
INSERT INTO Sales_Planning
(Time_Stamp, Campaign, Expected_Sales)
VALUES 
("2019-11-04", "Campaign01", "300"),
("2019-11-04", "Campaign02", "300"),
("2019-11-04", "Campaign03", "300"),
("2019-11-04", "Campaign04", "300"),
("2019-11-05", "Campaign01", "600"),
("2019-11-05", "Campaign02", "800"),
("2019-11-05", "Campaign03", "300"),
("2019-11-05", "Campaign04", "300"),
("2019-11-06", "Campaign01", "300"),
("2019-11-06", "Campaign02", "200"),
("2019-11-06", "Campaign03", "400"),
("2019-11-06", "Campaign04", "500");

In the table I have the history of the Sales_Planning of different campaigns.
As you can see every day the Expected_Sales are stored into this table using a Time_Stamp.
Ideally, once the Expected_Sales are inserted they never change.
However, sometimes the Expected_Salse are changed.

---

Now, I want to identify the Campaigns that have changed their Expected_Sales for example between
Time_Stamp_A 2019-11-04
Time_Stamp_B 2019-11-06

The result should look like this:

Campaign       Time_Stamp_A      Time_Stamp_B     Expected_Sales_A     Expected_Sales_B
Campaign02      2019-11-04        2019-11-06           300                  200
Campaign03      2019-11-04        2019-11-06           300                  400
Campaign04      2019-11-04        2019-11-06           300                  500

The closest I came so far is this query:

SELECT
Campaign,
Time_Stamp,
Expected_Sales,
(CASE WHEN Time_Stamp = "2019-11-04" THEN "Time_Stamp_A" ELSE "Time_Stamp_B" END) AS Time_Stamp
FROM Sales_Planning
WHERE 
Time_Stamp = "2019-11-04" 
OR Time_Stamp = "2019-11-06";

What do I need to change in my SQL to get the result I need?

Gordon Linoff :

Is this what you want?

SELECT sp1.Campaign, sp1.Time_Stamp, sp1.Expected_Sales,
       sp2.Time_Stamp, sp2.Expected_Sales
FROM Sales_Planning sp1 JOIN
     Sales_Planning sp2
     ON sp1.campaign = sp2.campaign AND
        sp1.Time_Stamp = '2019-11-04' AND 
        sp2.Time_Stamp = '2019-11-06'
WHERE sp1.Expected_Sales <> sp2.Expected_Sales;

This seems to return what you want.