getting parent key

Hi,
My Input is like below

Parent_code child_code CHILD_SK PARENT_SK
               00.1        1
ABC.20         ABC         2       null
ABC.20         CDE.20      3       null
ABC.20         EFG.20      4       null
BDE.20         ABC.20      5       null


i want to update parent_sk as below based upon join from parent_code with child_code:

so output should be like below


Parent_code child_code CHILD_SK PARENT_SK
               00.1        1       null
ABC.20         ABC         2       5
ABC.20         CDE.20      3       5
ABC.20         EFG.20      4       5
BDE.20         ABC.20      5       5

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Thanks
sam2929Asked:
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sdstuberConnect With a Mentor Commented:
I'm afraid I don't understand the join conditions

why is the last row updated to 5?


getting the other rows is easy

update yourtable a SET parent_sk = (select child_sk from yourtable  b
where a.parent_code = b.child_code
)
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sdstuberCommented:
I probably need a rule for the first row too.  The update above will set it to NULL, but sort of incidentally.  If there is something more explicit, please explain.
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sam2929Author Commented:
My bad it should be null
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sdstuberCommented:
"it"  ?

Does "it" refer to the first row or the last row?  

If both,  then the update above should do it for you.

If not, can you be more specific? And since there were 2, which ever one you didn't mean, can you explain the rule for that one too?
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