Update to previous query

Question

About every 2 or 3 hours, I can be heard for approximately 3 or 4 minutes before I go silent. Does that help?

Answer 1

Hi,
x = y
is not true if either x or y, or both, is NULL.
Whenever you have a question, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
In the case of a DML operation (such as UPDATE) the sample data should show what the tables are like before the DML, and the results will be the contents of the changed table(s) after the DML.
Explain, using specific examples, how you get those results from that data.
Is unique_id really unique?  Can it be NULL?
Always say what version of Oracle you're using (e.g. 11.2.0.2.0).
See the forum FAQ: https://forums.oracle.com/message/9362002
You might want something like this:
UPDATE  table_1
SET     doc_title  = 'Data'
WHERE   unique_id  IN (
                          SELECT  t1.unique_id
                          FROM    table_1  t1
                          JOIN    table_2  t2  ON   t1.unique_id  = t2.unique_id
                          WHERE   t1.doc_title  IS NULL
                          AND     t2.doc_type   = 'AP'
AND     doc_title  IS NULL    -- Maybe
I can't be sure without some sample data, desired results and reasons.