Constraint naming standard

The Big Picture

• We can quickly identify and fix any errors.
• We can reliabily modify or drop constraints

Abbreviations

Format of constraint name

In reality, this won't be possible because of the character limitation on names inside oracle. When the name is too long, we will follow these two steps in order:

1. Abbreviate the table name with the table's initials (e.g. users -> u and users_contact -> uc).
2. Truncate the column name until it fits.

Notes:

• If you have to abbreviate the table name for one of the constraints, abbreviate it for all the constraints
• If you are defining a multi column constraint, try to truncate the two column names evenly

Example

create table example_topics (
       topic_id    integer
		   constraint example_topics_topic_id_pk
		   primary key
);

create table constraint_naming_example (
       example_id		      integer
				      constraint cne_example_id_pk
				      primary key,
       one_line_description	      varchar(100)
				      constraint cne_one_line_desc_nn
				      not null,
       body			      clob,
       up_to_date_p		      char(1) default('t')
				      constraint cne_up_to_date_p_check
				      check(up_to_date_p in ('t','f')),
       topic_id			      constraint cne_topic_id_nn not null
				      constraint cne_topic_id_fk references example_topics,
       -- Define table level constraint
       constraint cne_example_id_one_line_unq unique(example_id, one_line_description)
);

Why it's good to name primary keys

SQL> set autotrace traceonly explain;


SQL> select * from constraint_naming_example, example_topics 
where constraint_naming_example.topic_id = example_topics.topic_id;

Execution Plan
----------------------------------------------------------
   0	  SELECT STATEMENT Optimizer=CHOOSE
   1	0   NESTED LOOPS
   2	1     TABLE ACCESS (FULL) OF 'CONSTRAINT_NAMING_EXAMPLE'
   3	1     INDEX (UNIQUE SCAN) OF 'EXAMPLE_TOPICS_TOPIC_ID_PK' (UNI
	  QUE)

Naming not null constraints is optional...

About Naming the not null constraints
Though naming "not null" constraints doesn't help immeditately in error debugging (e.g. the error will say something like "Cannot insert null value into column"), we recommend naming not null constraints to be consistent in our naming of all constraints.