Select rows where column b is found in column a

Question

I have a table that looks like this...

------------------------------------
| sku            | superseded_sku  |
------------------------------------
| PartA          | PartC           |
| PartB          | PartC           |
| PartC          | PartD           |
| PartD          |                 |

I need to write a query that will show me all rows where an entry from coumn B appears in column A. For example here it would give me the following...

------------------------------------
| sku            | superseded_sku  |
------------------------------------
| PartC          | PartD           |
| PartD          |                 |

I have tried this...

SELECT x.sku, x.superseded_sku FROM table x
JOIN table y ON y.sku = x.sku
WHERE y.superseded_sku = x.sku

but it returns nothing and now I don't know where to go from here

Answer 1

Think this query will give you the result:

SELECT x.sku, x.superseded_sku FROM table x
JOIN table y ON y.sku = x.superseded_sku