1. Introducing SQL : Object Naming Rules
 
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Object Naming Rules
The rules for naming database objects (such as tables, columns, and views) are as follows:
Names can contain only alphanumeric characters and must begin with an alphabetic character or an underscore (_). Database names must begin with an alphabetic character, and cannot begin with an underscore.
Case significance (upper or lower) is determined by the settings for the database in which the object is created (ANSI/ISO Entry SQL-92-compliant) and differs for regular and delimited identifiers.
Names can contain (but cannot begin with) the following special characters: 0 through 9, #, @, and $. Names specified as delimited identifiers (in double quotes) can contain additional special characters. Database objects cannot begin with the letters, ii. This prefix is reserved for use by the DBMS Server.
For details on valid user names, see User Names.
For details about delimited identifiers, see Regular and Delimited Identifiers.
The maximum length of names for the following objects is 256 bytes:
Column
Constraint
Index
Synonym
Table
Vector always installs with the UTF8 character set, so the maximum length of a name may be less than 256 characters if some glyphs use multiple bytes.
The maximum length of names for the following objects is 32 bytes:
Database
Location
Node
Group
Owner
Profile
Role
Schema
User
Database names must be unique to 24 bytes.
Avoid assigning reserved words as object names. A list of reserved words can be found in the in the appendix “Keywords” in the Ingres SQL Reference Guide
For ANSI/ISO Entry SQL-92 compliant databases, the maximum length of an object name is 18 bytes.