Numeric data types

Informix®

Informix supports several data types to store numbers:

Table 1. Informix numeric data types
Informix data type Description
SMALLINT 16 bit signed integer
INTEGER 32 bit signed integer
BIGINT 64 bit signed integer
INT8 64 bit signed integer (replaced by BIGINT)
DECIMAL Equivalent to DECIMAL(16)
DECIMAL(p) Floating-point decimal number (max precision is 32)
DECIMAL(p,s) Fixed-point decimal number (max precision is 32)
MONEY Equivalent to DECIMAL(16,2)
MONEY(p) Equivalent to DECIMAL(p,2) (max precision is 32)
MONEY(p,s) Equivalent to DECIMAL(p,s) (max precision is 32)
REAL / SMALLFLOAT 32-bit floating point decimal (C float)
DOUBLE PRECISION / FLOAT[(n)] 64-bit floating point decimal (C double)

SQLite

SQLite 3 supports INTEGER (8 byte integer) and REAL (8 byte floating point) as native types to store numbers, but allows also synonyms:

Table 2. SQLite numeric data types and supported synonyms
Supported synonyms SQLite type affinity
INT, INTEGER, TINYINT, SMALLINT, MEDIUMINT, BIGINT, UNSIGNED BIG INT, INT2, INT8 INTEGER (8 bytes!)
REAL, DOUBLE, DOUBLE PRECISION, FLOAT REAL (8 bytes!)
DECIMAL(p,s), NUMERIC NUMERIC (based on REAL)
Important: Exact decimal types like DECIMAL(p,s) may be stored as floating point numbers (REAL), INTEGER or TEXT types, according to the type affinity selected by SQLite. When converted to floating point type, data loss and rounding rule differences are possible with SQLite.

Solution

Informix numeric types are not translated by the SQLite database driver: The numeric types are used as is when creating tables, since SQLite supports a wide range of type synonyms.

Since SQLite 3 does not have exact decimal types like DECIMAL(p,s), you must pay attention to the rounding rules and data loss when using numbers with many significant digits. Arithmetic operations like division have different results than with Informix. It is better to fetch the original column value into a DECIMAL variable, and do arithmetic operations in the application program.

The numeric types translation can be controlled with the following FGLPROFILE entries:
dbi.database.dsname.ifxemul.datatype.smallint = { true | false }
dbi.database.dsname.ifxemul.datatype.integer = { true | false }
dbi.database.dsname.ifxemul.datatype.bigint = { true | false }
dbi.database.dsname.ifxemul.datatype.int8 = { true | false }
dbi.database.dsname.ifxemul.datatype.decimal = { true | false }
dbi.database.dsname.ifxemul.datatype.money = { true | false }
dbi.database.dsname.ifxemul.datatype.float = { true | false }
dbi.database.dsname.ifxemul.datatype.smallfloat = { true | false }
For more details see IBM Informix emulation parameters in FGLPROFILE.