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ddl

Better to be safe than sorry…

I’ve always been worried about taking a script that is fine to run in my non-production environments (in particular a DROP script) and accidentally running it in a Production environment, shortly followed by the typing up of a fresh resume to look for a new job once the mistake is discovered Smile

DDL triggers – interesting results

This question came in on AskTom, yielding a very interesting result when it comes to DDL triggers. To set the scene, I’ll first create a table called T which is just a copy of SCOTT.EMP

Duplicate constraints are impossible right ?

Here’s a very simple example of a table called PARENT being a (surprise surprise) parent in a referential integrity relationship to a (drum roll for my choice of name) CHILD table


SQL> create table parent ( p int, constraint PAR_PK primary key (p) );

Table created.

SQL> create table child ( c int,
  2        p int
  3      );

Table created.

SQL> alter table child add constraint fk1 foreign key ( p ) references parent ( p );

Table altered.

That is all as we would expect, and similarly, if I inadvertently try to add the same foreign key constraint, I’ll get an error