Question

I need write an update statement that used multiple tables to determine which rows to update, since in Oracle, multiple tables aren’t allowed. The following query will return a ‘ORA-00971: Missing SET keyword’ error

UPDATE   TABLE1 a,   TABLE2 b SET   a.COL1 = 'VALUE' WHERE   a.FK = b.PK   AND b.COL2 IN ('SET OF VALUES') 

Looking up the UPDATE statement syntax on oracle, I found the following link, which shows that you can use a subquery in place of a table name.

When I tried to write the query like this, I got a ‘ORA-01779: Cannot modify a column which maps to a non key-preserved table’

UPDATE   (     SELECT       a.COL1     FROM       TABLE1 a,       TABLE2 b     WHERE       a.FK = b.PK       AND b.COL2 IN ('SET OF VALUES')   ) update_tbl SET   update_tbl.COL1 = 'VALUE' 

I did rewrite the query (show below) using an EXISTS statement instead and it works fine, but would still like to know how this is done.

UPDATE   TABLE1 update_tbl SET   update_tbl.COL1 = 'VALUE' WHERE   EXISTS (     SELECT       1     FROM       TABLE1 a       TABLE2 b     WHERE       a.FK = b.PK       AND b.COL2 IN ('SET OF VALUES')       AND update_tbl.PK = a.PK   ) 

Thanks! -Nate

Answer 1

Another option:

UPDATE TABLE1 a SET a.COL1 = 'VALUE' WHERE a.FK IN ( SELECT b.PK FROM TABLE2 b   WHERE b.COL2 IN ('SET OF VALUES') ) 

Your second example would work if (a) the view included the declared PK of TABLE1:

UPDATE   (     SELECT       a.COL1, a.PKCOL     FROM       TABLE1 a,       TABLE2 b     WHERE       a.FK = b.PK       AND b.COL2 IN ('SET OF VALUES')   ) update_tbl SET   update_tbl.COL1 = 'VALUE' 

… and (b) TABLE1.FK was a declared foreign key to TABLE2

(By declared I mean that a constraint exists and is enabled).