DataFlex supports using Unicode data in your applications. For developers running prior revisions of DataFlex (19.1 and eariler) on SQL databases, and want to make their application Unicode-ready, some steps may need to be taken to make those databases able to appropriately handle Unicode data.
We outline below the basic actions to prepare a DataFlex database environment to work with Unicode. Note that once databases are set to be Unicode-capable and Unicode data is stored in them, these changes cannot be reversed without the risk of losing information.
To migrate an existing SQL database to become Unicode capable, take the following steps:
Note: The DataFlex SQL drivers fully support both non-Unicode and Unicode databases. Migration is not a requirement. Leaving databases as non-Unicode capable just means it cannot store Unicode data.
Existing SQL databases created by DataFlex versions prior to DataFlex 2021 may be in either ANSI or OEM format. ANSI tables support Unicode data, however, OEM tables do not. OEM tables are only supported in DataFlex 2021 and higher for backward compatibility.
In order to make your database Unicode-capable, you will need to migrate any OEM tables to ANSI. Read how to handle OEM data in DataFlex so you can adjust your applications accordingly.
Table Character Format in DataFlex
The process of converting databases to Unicode-capable will depend on the type of SQL database backend being used. Before going through details on the conversion, it will be interesting to review what different database may require to properly handle Unicode data.
The various available SQL database systems can handle Unicode data in different ways. In general, there are two main methods:
In MySQL, for example, a database can be created with character set latin1 or utf8mb4. In a latin1 database, char/varchar columns will be stored as latin1 (ANSI) and cannot store Unicode characters. In a utf8mb4 database, char/varchar columns will be stored as utf8 and can store Unicode data.
Each database system will have their way to work with Unicode data. Here is how some of the most popular databases enable the use of Unicode:
Special Unicode data types - the N types (nchar,nvarchar).
In SQL Server 2019, Unicode data can also be stored in char/varchar columns by setting the collating of the column to a utf8 collating.
Character set setting
Has both special Unicode types (Graphic types) and codeset setting.
The following links include an overview on setting up a database for the different database environments:
To make SQL Server databases Unicode-capable all char/varchar columns should be changed to nchar/nvarchar.
Columns of the text data type should be changed to nvarchar(max) since Microsoft already indicated that text/ntext data types will be removed in a future version of SQL Server.
Before changing the data type, make sure all OEM tables have been migrated to ANSI.
Once all tables are ANSI, you will have a few options on how to change char/varchar columns to nchar/nvarchar:
The following program illustrates how to convert all char/varchar columns to nchar/nvarchar for all tables in a workspace:
Get_Attribute DF_FILE_NEXT_USED of hTable to hTable
If (hTable > 0 and (hTable <> 50)) Begin
Send ConvertTableToUnicodeNTypes hTable
Until (hTable = 0)
Procedure ConvertTableToUnicodeNTypes Handle hTable
Integer iNumColumns iColumn iDFType iNativeType
String sColumnName sNativeTypeName
// trap open table error so it's not fatal
Move False to Err
Send Ignore_All to Error_Object_Id
Move Err to bTableOpenError
Send Trap_All of Error_Object_Id
If (bTableOpenError = False) Begin
Get_Attribute DF_FILE_ROOT_NAME of hTable to sTableName
Get_Attribute DF_FILE_LOGICAL_NAME of hTable to sLogicalName
Get_Attribute DF_FILE_DRIVER of hTable to sDriverName
If (sDriverName = 'MSSQLDRV') Begin
Get_Attribute DF_FILE_NUMBER_FIELDS of hTable to iNumColumns
For iColumn from 1 to iNumColumns
Get_Attribute DF_FIELD_NAME of hTable iColumn to sColumnName
Get_Attribute DF_FIELD_TYPE of hTable iColumn to iDfType
Get_Attribute DF_FIELD_NATIVE_TYPE of hTable iColumn to iNativeType
Get_Attribute DF_FIELD_NATIVE_TYPE_Name of hTable iColumn to sNativeTypeName
If (iDFType = DF_ASCII) Begin
If (iNativeType = SQL_CHAR) Begin
// Convert char to nchar
Set_Attribute DF_FIELD_NATIVE_TYPE of hTable iColumn to SQL_WCHAR
If (iNativeType = SQL_VARCHAR) Begin
// Convert varchar to nvarchar
Set_Attribute DF_FIELD_NATIVE_TYPE of hTable iColumn to SQL_WVARCHAR
If (iDFType = DF_TEXT) Begin
If (iNativeType = SQL_LONGVARCHAR) Begin
// Convert text to ntext
Set_Attribute DF_FIELD_NATIVE_TYPE of hTable iColumn to SQL_WLONGVARCHAR
If (iNativeType = SQL_VARCHARMAX) Begin
// Convert varcharmax to nvarcharmax
Set_Attribute DF_FIELD_NATIVE_TYPE of hTable iColumn to SQL_WVARCHARMAX
Database systems without special Unicode data types use code set/collating settings to define a database as Unicode or Non-Unicode database. In MySQL, for example, a database can be created with character set latin1 or utf8mb4:
Making a non-Unicode database Unicode-capable in this case means that the code set or the collating of the database must be changed.
It is important to note that DataFlex SQL drivers will work with both Unicode and non-Unicode databases. The drivers will take care of character set conversions as needed.
In order to make a non-Unicode database Unicode-capable, you may use one of the following methods:
This varies with database system (see the Further Information on Other Databases and Unicode section below). Often this can be done on a database, table, or column level.
Be aware that changing the collating of a database does NOT change the collating of the existing data. Existing data must still be converted. You may accomplish that by exporting data in the current collating and importing it once the new collating is set, or using another technique available in the database system – for example, executing an ALTER TABLE [table] CONVERT TO CHARACTER SET [charset] COLLATE [collate] statement in MySQL.
Here are some useful links with information about the various database systems that may be used with DataFlex 20 and their Unicode handling capability.
SQL server 2019 supports Unicode data in char/varchar columns by setting the collating to an utf8 collating.
The links below contain information on how to change the collation of char/varchar columns to an utf8 collating:
Further information on data types and character set in SQL Server:
The links below contain information on how to convert a MySQL ANSI (Latin1) database to Unicode (utf8mb4) database:
Further information on character set and collating in MySQL:
The links below contain information on character set and collating in MariaDB:
The links below contain information on character set and migration in Oracle:
The links below contain information on character set in PostgreSQL:
Working with DataFlex 2021