MS Access SQL - how to join table based on another column in the same table

In my database, we have a MASTER_SKU_DATA table, which includes the SKU, Description, and Deposit_SKU (which is another SKU, with its own record in the same MASTER_SKU_DATA table)

We may have an example SKU of 12345, with supplier ID 999, and a deposit SKU of 10001. The Deposit SKU normally will have a different supplier, so I want to create a query which will join the table back onto itself to provide the other Supplier ID (and join a pricing table as well)

An example set of data from the MASTER_SKU_DATA table:
(SKUP is the original database table, MASTER_SKU_DATA helps to join a few other fields such as Supplier Name for easy access to related information)

Example from MASTER_PRICE_COST table:

Example result:

I created a very simple query called [DepositSKUs], which uses this query:

SELECT DISTINCT SKUP.DEPOSIT_SKU FROM SKUP WHERE (SKUP.DEPOSIT_SKU Is Not Null)

Now I'm trying to run another query of the MASTER_SKU_DATA, joining our MASTER_PRICE_COST as well, but only where the MASTER_SKU_DATA is one of those Deposit_SKUs. I'm using the query below:

SELECT  MASTER_SKU_DATA.SKU,
        MASTER_SKU_DATA.Description,
        MASTER_SKU_DATA.Active_Flag,
        MASTER_SKU_DATA.ID_Supplier,
        MASTER_SKU_DATA.Supplier_Name,
        MASTER_PRICE_COST.PRICE_START_DATE,
        MASTER_PRICE_COST.PRICE_END_DATE,
        MASTER_PRICE_COST.PRICE
FROM MASTER_SKU_DATA 
LEFT JOIN MASTER_PRICE_COST ON 
    MASTER_SKU_DATA.SKU = MASTER_PRICE_COST.SKU
WHERE MASTER_SKU_DATA.SKU IN (SELECT DepositSKUs.DEPOSIT_SKU FROM DepositSKUs)

However, when I try to run this query, it keeps freezing my Microsoft Access, and doesn't seem to work properly and I'm not sure why.

I've been trying to research this and found some tips, indicating that when you use a query where a value is IN this list, it takes more processing power because it's checking for each SKU if SKU = <value1> OR SKU = <value2> etc..
I couldn't find any solutions however, on how to do this same filter through the JOIN instead.

I've tried to test things such as joining the MASTER_SKU_DATA AS [DEP_SKUD], but can't seem to get the syntax right and I'm not sure where to look further.

Could you please let me know if there is a way I could fix this query?
If there is a different function or feature which I can google and research further, please let me know - just stumped and not sure where I'm steering wrong.

It looks like you're trying to overthink the solution. I am assuming that SKU is the primary key so you will never have a null value. Try this SQL where I have joined MASTER_SKU_DATA to itself via the Deposit_SKU:

SELECT MASTER_SKU_DATA.Deposit_SKU,
       MASTER_SKU_DATA_1.Description,
       MASTER_SKU_DATA_1.ID_Supplier,
       MASTER_PRICE_COST.PRICE_START_DATE,
       MASTER_PRICE_COST.PRICE_END_DATE,
       MASTER_PRICE_COST.Price
FROM MASTER_SKU_DATA 
INNER JOIN (
  MASTER_SKU_DATA AS MASTER_SKU_DATA_1 
  INNER JOIN MASTER_PRICE_COST 
  ON MASTER_SKU_DATA_1.SKU = MASTER_PRICE_COST.SKU
) 
  ON MASTER_SKU_DATA.Deposit_SKU = MASTER_SKU_DATA_1.SKU;

Based on the data you provided, it produces the example result that you also provided.

What you are trying to do is known as a reflexive join. This is a join between two instances of the same table, where a foreign key of one instance references the primary key of the other instance. If you do some research on reflexive joins, you should get a tutorial. Unfortunately, when I did the search, none of the examples that popped up were cases that involved MS ACCESS. They were all for some other DBMS.

Here is my attempt (not debugged) to provide a single query to do what you want:

SELECT
    M.Deposit_SKU,
    S.Description,
    S.Supplier_ID,
    P.PRICE_START_DATE,
    P.PRICE_END_DATE,
    P.PRICE
FROM (
    MASTER_SKU_DATA S 
    INNER JOIN MASTER_SKU_DATA M
        ON S.SKU = M.Deposit_SKU)
    INNER JOIN MASTER_PRICE_COST P
        ON S.SKU = P.SKU

There are several points to be noted here.

The Deposit_SKU field could contain three kinds of value. It could contain a NULL, or it could contain a valid value, or it could contain an invalid value. An invalid value would be one where there is no corresponding record with a matching SKU. That would be a clue that the data is messed up, somehow. This query will drop out records with a NULL or an invalid value in the Deposit_SKU field.

I chose to use an INNER JOIN with the price table instead of the LEFT JOIN you chose. My choice could be incorrect, if there are some SKUs in the master table with no entry in the price table. It is generally a little faster to use INNER JOIN, when it produces correct results.

In general, reflexive joins can't be done without table aliases. I used one letter abbreviations for table aliases. That's my habit. Suit yourself.

I chose to select M.Deposit_SKU instead of S.SKU so that the column header in the output would match your example.