About NUMERIC and DECIMAL Data Types

From InterBase

Go Up to Method One: In-place Migration

If you back up a NUMERIC or DECIMAL column with a precision greater than 9 (for example, NUMERIC(12,2)) in an InterBase 5 or earlier database and restore the database as InterBase 6 and later, the column is still stored as DOUBLE PRECISION. Because InterBase does not allow data type conversions that could potentially result in data loss, you cannot use the ALTER COLUMN statement to change the column data type from DOUBLE PRECISION to INT64. To migrate a DOUBLE PRECISION column to an INT64 column, you must create a new INT64 column and copy the contents of the older column into it.

In InterBase 6 and later dialect 3, when you create a NUMERIC or DECIMAL column with a precision of greater than 9, data in it is automatically stored as an INT64 exact numeric.

If you want NUMERIC and DECIMAL data types with a precision greater than 9 to be stored as exact numerics, you must take some extra steps after migrating to dialect 3. The following sections tell you how to decide whether you really need to take these steps and how to perform them if you decide you want the exact numerics.


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