CHAR and VARCHAR data types
Informix®
Informix supports the following character data types:
| Informix data type | Description |
|---|---|
CHAR(n) |
SBCS and MBCS character data (max is 32767 bytes) |
VARCHAR(n[,m]) |
SBCS and MBCS character data (max is 255 bytes) |
NCHAR(n) |
Same as CHAR, with specific collation
order |
NVARCHAR(n[,m]) |
Same as VARCHAR, with specific collation
order |
LVARCHAR(n) |
max size varies depending on the IDS version |
With Informix, both
CHAR/VARCHAR and NCHAR/NVARCHAR data types can be used to store
single-byte or multibyte encoded character strings. The only difference between
CHAR/VARCHAR and NCHAR/NVARCHAR is in how they use sorting:
N[VAR]CHAR types use the collation order, while [VAR]CHAR types
use the byte order.
The character set used to store strings in
CHAR/VARCHAR/NCHAR/NVARCHAR columns is defined by the DB_LOCALE environment
variable.
Informix uses Byte Length Semantics (the size
N that you specify in [VAR]CHAR(N) is expressed in bytes, not characters as in some
other databases)
SQLite
SQLite 3 provides the TEXT native data type with no strict size limitation.
SQLite allows the CHAR(n), VARCHAR(n), NCHAR(n)
and NVARCHAR(n) type names to be used, but actually stores the data in a
TEXT native type.
SQLite treats empty strings as NOT NULL values like Informix.
VARCHAR and
CHAR values by taking trailing blanks into account. Informix always ignores trailing blanks when comparing
CHAR/VARCHAR values. SQLite supports only the UTF-8 character encoding. Thus, client applications must provide UTF-8 encoded strings.
Solution
The database interface supports character string variables in SQL statements for input (BDL
USING) and output (BDL INTO).
CHAR and
VARCHAR comparison in SQLite takes trailing blanks into account. As result, some
queries returning rows with Informix may not return the
same result set with SQLite. When creating a table in SQLite, you can change the default collation
rule to force the database engine to trim trailing blanks before comparing
CHAR/VARCHAR values, by specifying COLLATION RTRIM in the column
definitions. When creating a table from a Genero program, if Informix emulation is enabled for the CHAR/VARCHAR types, the SQLite
database driver adds automatically COLLATE RTRIM after the CHAR(N)
or VARCHAR(N) type, to get the same comparison semantics as Informix. Regarding character sets, the SQLite database driver automatically converts character strings used in the programs to/from UTF-8 for SQLite.
SQLite uses character length semantics: When you define a CHAR(20)
and the database character set is multibyte, the column can hold more bytes/characters than the Informix CHAR(20) type, when using byte
length semantics.
When using a multibyte character set (such as UTF-8), define database columns with the size in character units, and use character length semantics in BDL programs with FGL_LENGTH_SEMANTICS=CHAR.
When extracting a database schema from a SQLite database, the fgldbsch schema extractor uses the
size of the column in characters, not the octet length. If you have created a CHAR(10
(characters) ) column a in SQLite database using the UTF-8 character set, the .sch file
will get a size of 10, that will be interpreted following FGL_LENGTH_SEMANTICS, as a number of bytes
or characters.
See also the section about Localization.
CHAR/VARCHAR type translation can be controlled with the following FGLPROFILE
entries:dbi.database.dsname.ifxemul.datatype.char = { true | false }
dbi.database.dsname.ifxemul.datatype.varchar = { true | false }