Question

How to insert a number into the table, only if the table does not already have that number in it?

I am looking for specific SQL code, not really sure how to approach this. Tried several things, nothing’s working.

EDIT

Table looks like this:

PK   ID    Value
1     4     500
2     9     3

So if I am trying to INSERT (ID, Value) VALUES (4,100) it should not try to do it!

Answer 1

Try MERGE statement:

MERGE INTO tbl USING
    (SELECT 4 id, 100 value FROM dual) data
ON (data.id = tbl.id)
WHEN NOT MATCHED THEN
    INSERT (id, value) VALUES (data.id, data.value)