Special Character Sets

The character set NONE is a special character set in Firebird.It can be characterized such that each byte is a part of a string, but the string is stored in the system without any clues about what constitutes any character: character encoding, collation, case, etc. are simply unknown.It is the responsibility of the client application to deal with the data and provide the means to interpret the string of bytes in some way that is meaningful to the application and the human user.

Data in OCTETS encoding are treated as bytes that may not be interpreted as characters.OCTETS provides a way to store binary data.The database engine has no concept of what it is meant to do with a string of bytes in OCTETS, other than store and retrieve it.Again, the client side is responsible for validating the data, presenting them in formats that are meaningful to the application and its users and handling any exceptions arising from decoding and encoding them.CHAR and VARCHAR with character set OCTETS have synonyms BINARY and VARBINARY.

Each character set has a default collation (COLLATE) that specifies the collation order (or, collation sequence, or collating sequence).Usually, it provides nothing more than ordering based on the numeric code of the characters and a basic mapping of upper- and lower-case characters.If some behaviour is needed for strings that is not provided by the default collation and a suitable alternative collation is supported for that character set, a COLLATE collation clause can be specified in the column definition.

A COLLATE collation clause can be applied in other contexts besides the column definition.For comparison operations, it can be added in the WHERE clause of a SELECT statement.If output needs to be sorted in a special alphabetic sequence, or case-insensitively, and the appropriate collation exists, then a COLLATE clause can be included with the ORDER BY clause when rows are being sorted on a character field and with the GROUP BY clause in case of grouping operations.