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To achieve a higher performance for the data query in external data sources, you can define parameters. Especially when you have tables and feature classes with a huge set of datasets. The parameter is specified within the SQL statement. The following example shows how a parameter is used for an Oracle connection:

 

Add the field, which serves as parameter to the SQL statement. The parameter field should be a unique key field.

Select ColumnX, ColumnY, ColumnZ from Table1

where ColumnX = :param

 

A parameter for the Oracle connection consists of a : and the Parameter name.

Note: The syntax of the parameter is different depending on database type and database provider.

 - When you use an Oledb Connection for your Oracle database, you have to use ? as parameter.

 - When you use a SQL Connection for your SQL database you have to use @ as parameter.

 

It is not enough to add the parameter to the SQL statement. It also has to be defined as column in the table. For that, specify Name, Expression, Size and Type. Expression includes the data column from which the parameter is provided. Type and size specifies the data type and the length of the parameter.

 

To ensure a correct query on the data, you have to set the data source property ReconnectOnEachRow to True. If you don't set this property to True, the parameter is only valid for the first data entry.