Updating SQL Error ORA-01427: single-row subquery returns more than one row

Question

I have this SQL statement to update column aisle from table itemloc_tmp from aisle from table itemloc_tbl in SQLPLUS, and it keeps returning the error like in the topic.

Update: This is sample data from itemloc_tmp

ITEM_ID       SID SEC AIS
------------- --- --- ---
0007AAAAAAAAA     AA3 12
0007BBBBBBBBB     BB2 13
0007CCCCCCCCC     CC8 11

This is sample from itemloc_tbl

ITEM_ID       SID SEC AIS
------------- --- --- ---
0007AAAAAAAAA
0007BBBBBBBBB     
0007CCCCCCCCC      

This is the my sql statement

    UPDATE ct.itemloc_tbl t1 SET 
    t1.aisle = (SELECT t2.aisle FROM ct.itemloc_tmp t2 WHERE t2.item_id = t1.item_id)
    WHERE t1.item_id IN (SELECT t2.item_id FROM ct.itemloc_tmp t2 WHERE t2.item_id = t1.item_id) 

So, I want to update aisle column from itemloc_tmp to itemloc_tbl , but the statement above does not work. Would anyone point out where I was wrong?

Answer 1

You can limit the rows being updated. Here are two ways. The first uses rownum = 1 :

UPDATE ct.itemloc_tbl t1 SET 
    SET t1.aisle = (SELECT t2.aisle FROM ct.itemloc_tmp t2 WHERE t2.item_id = t1.item_id AND rownum = 1)
    WHERE EXISTS (SELECT 1 FROM ct.itemloc_tmp t2 WHERE t2.item_id = t1.item_id);

The second uses an aggregation function:

UPDATE ct.itemloc_tbl t1 SET 
    SET t1.aisle = (SELECT MAX(t2.aisle) FROM ct.itemloc_tmp t2 WHERE t2.item_id = t1.item_id)
    WHERE EXISTS (SELECT 1 FROM ct.itemloc_tmp t2 WHERE t2.item_id = t1.item_id);

Either of these fix the proximal cause of the error, which is the subquery returning more than one row. However, you need to decide what you really want for the assignment. If an "arbitrary" value is fine, then these work.