Database Naming Conventions
Common Network Information Service
Editors: Paweł Gruszczyński PSNC, Damian Mierzwiński PSNC
1. Introduction
The aim of this document is to present database naming conventions used in cNIS project.
First part of this document describe standard naming conventions used in relational databases.
Second part confront this standard approach with cNIS conventions based on Hibernate ORM
tool. Last section provide short recommendations for developers of cNIS project.
This document is dedicated for a wide audience, including developers, programmers, people
who are responsible for tests and authors of the software documentation.
2. Standard naming conventions
2.1 Tables
2.1.1 Plural Names
Table names should be plural. For table names with multiple words, only the last word should
be plural.
2.1.2 Prefixes
Table prefixes can help organize tables into related groups or distinguish them from other
unrelated tables. Avoid prefixes like "tbl" or "TBL_" as these are just redundant and
unnecessary.
2.1.3 Notation
Table name:
 should be lowercased

for word separator and prefixes '_' sign should be used

should not contain numbers

should not contain spaces.
2.1.4 Junction (Intersection Tables)
Junction tables, which handle many to many relationships, should be named by concatenating
the names of the tables (with '_' separator) that have a one to many relationship with the
junction table. Since this convention can result in lengthy table names, abbreviations
sometimes may be used at your discretion.
2.1.5 Other Table Naming Conventions
Use short, unambiguous names, using no more than one or two words. Avoid abbreviated,
concatenated, or acronymic names.
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2.2 Columns
Columns are members of the table, so they do not need the any mention of the table name in
the name. The primary key field is typically the only exception to this rule where including
the table name is justified so that you can have a more descriptive field name than just "id".
Just like with naming tables, avoid using abbreviations, acronyms or special characters. All
column names should use lowercased with '_' as word separator.
2.2.1 Identity Primary Key Fields
The primary key should be the singular table name suffixed with "_id".
2.2.2 Foreign Key Fields
Foreign key fields should have the same name as the primary key to which they refer. If
foreign key field is also primary key, then primary key rule is used.
2.2.3 Prefixes
Fields should not by prefixed with "fld_" or "col_" as it should be obvious in SQL statements
which items are columns (before or after the FROM clause).
2.2.4 Data Type Specific Naming
Boolean fields should be given names like "is_deleted", "has_permission", or "is_valid" so
that the meaning of the data in the field is not ambiguous. If the field holds date and/or time
information, the word "date" or "time" should appear somewhere in the field name. It is
sometimes appropriate to add the unit of time to the field name also, especially if the field
holds data like whole numbers.
2.3 Indexes
Since indexes are always related to a table or view, it makes the most sense to use the name of
the table or view, as well as the column(s) they index, in the index name, along with some
characters that specify the type of index it is. This naming convention also allows, if looking
at a list of indexes, to see the indexes ordered by table, then column, then index type.
2.3.1 Naming Convention
The
naming
convention
for
indexes
follows
this
structure:
{table_name}_{columns_indexed}{U/N} where "U/N" is for unique or non-unique. This
naming convention is unique among database objects, so adding characters to denote it being
an index, like "idx" is not necessary. The naming convention alone is self-documenting and
identifies it as an index. For indexes that span multiple columns, concatenate the column
names. If name is too long use abbreviations for column names.
2.4 Constraints
Constraints are at the field/column level so the name of the field the constraint is on should be
used in the name. The type of constraint (Check, Referential Integrity a.k.a Foreign Key,
Primary Key, or Unique) should be noted also. Constraints are also unique to a particular table
and field combination, so you should include the table name also to ensure unique constraint
names across your set of database tables.
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2.4.1 Naming Convention
The naming convention syntax for constraints looks like this: {constraint_type}_{table
name}_{field name}.
2.4.2 Prefixes
A two letter prefix gets applied to the constraint name depending on the type.
Constraint type
Prefix
Primary Key
pk
Foreign Key
fk
Check
ck
Unique
un
2.5 Views
Views follow many of the same rules that apply to naming tables.
2.5.1 Prefixes
View name should be prefixed with "vw_".
2.5.2 View Types
Naming views should be different depending on the type or purpose of the view. For simple
views that just join two or more tables with no selection criteria, view name should be
combined of names of the tables joined (also just name of the main table prefixed with "vw_"
could be used).
3. cNIS naming conventions
cNIS use Hibernate (version 3.2.6.ga) as data access library. Hibernate provide default
naming conventions which directly maps classes and properties names to tables and columns
names
without
any
changes.
To
override
this
behaviour
cNIS
use
org.hibernate.cfg.ImprovedNamingStrategy implementation of naming strategy which is very
close to the standard approach. Next sections compares ImprovedNamingStrategy with the
standard one.
3.1 Tables
3.1.1 Singular Names
Table names are generated automatically and are in the singular form. This simplifies the
overall Hibernate configuration and its maintenance. Words from the class name are split with
underscores and converted to lower case, e.g.:
NodeVersion class will be associated with table named node_version.
3.1.2 Junction (Intersection Tables)
Intersection tables are used to map many-to-many relations. The name of the intersection table
is specified by table attribute of the set element in Hibernate mapping files. Those names
should follow standard naming conventions.
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3.2 Columns
Table column names are generated automatically alike table names. Java persisted classes
properties in cNIS follow the standard naming convention, e.g.:
isVirtual, dateCreated, etc.
3.3 Indexes
Indexes are associated with one-to-many relations mapping and Java Map objects mapping.
Name of the index is specified by the index attribute and should follow standard naming
conventions for indexes.
3.4 Constrains
Constrains names are automatically generated by Hibernate tool and do not follow the
standard naming conventions. Primary key constraint name consists of a table name suffixed
by “_pkey” string. Other constraints are named randomly, according to the database policy.
3.5 Views
There are no views in the cNIS database schema.
4. Recommendations
It is recommended to use described here standard naming conventions when writing persistent
entities classes. Moreover, developers should be aware about Hibernate naming conventions
implementation used in cNIS (ImprovedNamingStrategy) and leave word splitting and
underscores inserting to Hibernate when it is only possible.
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