SQL Identifier Unquoted identifiers
Example
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.
- MS SQL:
@,$,#, and other Unicode letters (source) - MySQL:
$(source) - Oracle:
$,#, and other letters from database character set (source) - PostgreSQL:
$, and other Unicode letters (source)
Unquoted identifiers are case-insensitive. How this is handled depends greatly on SQL implementation:
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MS SQL: Case-preserving, sensitivity defined by database character set, so can be case-sensitive.
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MySQL: Case-preserving, sensitivity depends on database setting and underlying file system.
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Oracle: Converted to uppercase, then handled like quoted identifier.
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PostgreSQL: Converted to lowercase, then handled like quoted identifier.
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SQLite: Case-preserving; case insensitivity only for ASCII characters.
