Joining two tables on column A or column B in SQL - sql

Question

I have two tables called Plan and Actual. Every row in each table represents a unique item, and I need to find items that are in the Plan table, but not the Actual table, and vice versa.
There are three columns that uniquely identify each item, and the value for each of these columns may or may not be null.
For Example:
Say "Plan" looks like this:
ID_1 ID_2 ID_3
aaa Null Null
Null 111 Null
Null Null 123
bbb 222 Null
ccc Null 456
Null 333 789
ddd 444 202
Say "Actual" looks like this:
ID_1 ID_2 ID_3
aaa Null Null
Null 111 Null
bbb 222 Null
Null 333 789
Null 555 Null
eee Null 303
Using SQL, how can I identify the "In plan not in actual" rows of:
Null Null 123
ccc Null 456
ddd 444 202
And in "In actual not in plan" rows of:
Null 555 Null
eee Null 303
Thank you for your help!

Answer 1

If you are using ORACLE, you can use the operator MINUS. It will select rows in table "Plan" not in table "Actual".
SELECT ID_1, ID_2, ID_3
FROM Plan
MINUS
SELECT ID_1, ID_2, ID_3
FROM Actual;
If you are using SQL Server; use EXCEPT instead of minus.

Answer 2

You can use the LEFT JOIN. Below is the example with MySql.
In plan not in actual
SELECT Plan.* FROM Plan
LEFT JOIN Actual ON (Plan.ID_1 = Actual.ID_1 AND Plan.ID_2 = Actual.ID_2 AND Plan.ID_3 = Actual.ID_3)
WHERE Actual.ID_1 IS NULL AND Actual.ID_2 IS NULL AND Actual.ID_3 IS NULL;
In actual not in plan
SELECT Actual.* FROM Actual
LEFT JOIN Plan ON (Plan.ID_1 = Actual.ID_1 AND Plan.ID_2 = Actual.ID_2 AND Plan.ID_3 = Actual.ID_3)
WHERE Plan.ID_1 IS NULL AND Plan.ID_2 IS NULL AND Plan.ID_3 IS NULL;