| Unquoted identifiers Unquoted identifiers can use letters (a-z), digits (0-9), and underscore (_), and must start with a letter. Depending on SQL implementation, and/or database settings, other characters may be allowed, some even as the first character, e.g. Unquoted identifiers are case-insensitive. How this is handled depends greatly on SQL implementation:
MS SQL: Case-preserving, sensitivity defined by database character set, so can be case-sensitive.
MySQL: Case-preserving, sensitivity depends on database setting and underlying file system.
Oracle: Converted to uppercase, then handled like quoted identifier.
PostgreSQL: Converted to lowercase, then handled like quoted identifier.
SQLite: Case-preserving; case insensitivity only for ASCII characters.
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