Join on inequality in Power Query - excel

Question

I have been trying to answer this question
With the following data
+---------+---------+-----------+---------+
| Column1 | Column2 | Column3 | Column4 |
+---------+---------+-----------+---------+
| 1 | happy | 1-veggies | GHF |
| 1 | sad | 1-veggies | HGF |
| 2 | angry | 1-veggies | GHG |
| 2 | sad | 1-veggies | FGH |
| 3 | sad | 1-veggies | HGF |
| 4 | moody | 2-meat | FFF |
| 4 | sad | 2-meat | HGF |
| 5 | excited | 2-meat | HGF |
+---------+---------+-----------+---------+
OP was asking for a way of finding how many records there were which matched 'sad' and '1-veggies', and also had another record with the same value in column 1 and a code of GHF or FGH in column 4. The first two rows qualify, but the fourth row does not qualify because (if I understand correctly) it has the correct code, but in the same record as the one matching 'sad' and '1-veggies'. The count should be one.
I think the answer would have been fairly standard if this had been a SQL question - you would do a self-join with an equality on the first column and an inequality on the row number. In SQL it would look something like this:
create table Veggies
(
num integer,
emotion varchar(10),
food varchar(10),
code varchar(10),
seq integer
)
insert into Veggies
values
(1,'happy','1-veggies','GHF',1),
(1,'sad','1-veggies','HGF',2),
(2, 'angry' ,'1-veggies' ,'GHG',3),
(2, 'sad', '1-veggies', 'FGH',4),
(3, 'sad', '1-veggies', 'HGF',5),
(4, 'moody', '2-meat', 'FFF',6),
(4, 'sad', '2-meat', 'HGF',7),
(5, 'excited', '2-meat', 'HGF',8)
with t1 (num,seq)
as
(
select num,seq
from veggies
where emotion='sad' and food='1-veggies'
),
t2 (num,seq)
as
(
select num,seq
from veggies
where code='GHF' or code='FGH'
)
select *
from t1 inner join t2 on t1.num=t2.num and t1.seq<>t2.seq
I thought it might be possible to do the same thing (join on first column equal but row number unequal) in Power Query, but I have worked through the steps of getting the two queries with row numbers, and am stuck here:
I don't see any way of expressing an inequality and the documentation seems unhelpful. Does anyone have any inside knowledge on how to do this?

Answer 1

So although it looks as though you can't translate the SQL in the question directly into Power Query and replicate this in a single step
select *
from t1 inner join t2 on t1.num=t2.num and t1.seq<>t2.seq
you can split it into two steps as suggested by #Ron Rosenfeld.
To recap, the initial steps which hopefully were fairly straightforward were:
Establish a connection to the data as Table 1
Add an index column
Duplicate the table and call it Table 2
Filter table 1 by 'sad' and '1-veggies'
filter table 2 by 'GHF' or 'FGH'
Now join Table 2 to Table 1 using an inner join on Column 1:
and exclude rows that were in table 1 using a left anti join on the index column:
This leaves one row as required.