hi, there. i'm trying to write a SQL statement which does the following
things.
1. checks if data already exists in the database
2. if not, insert data into database otherwise skip.
for example, i'd like to insert a student called 'Michael Jordan' whose
ID is 'JORDANMICHAEL' only if the id, 'JORDANMICHAEL' does not already
exist in the database. anyway, my query looks like...
insert into student (studentid, fname, lname)
select 'JORDANMICHAEL', 'Michale', 'Jordan' from student where
studentid not in
(select studentid from student);
however, this does not seem to work. it does not insert data even if it
does not exist in the database. hmm!
any clue?
thanks.
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
