Dynamic SQL expressions

Dynamic formation of SQL expressions when updating data

TSQLDataDriverEh allows you to form Insert, Update and Delete SQL statements dynamically, immediately before sending a request to the server.

Use the subproperties of the DynaSQLParams property to customize the dynamic generation of SQL expressions.

The DynaSQLParams.Options property of the TDynaSQLOptionsEh type specifies which data change operations will be generated dynamically:

dsoDynamicSQLInsertEh

the operation of adding a record will be generated dynamically based on the filled properties UpdateTable, UpdateFields and SpecParams (for AUTO_INCREMENT_FIELD).

dsoDynamicSQLUpdateEh

the record change operation will be generated dynamically based on the filled in properties UpdateTable, UpdateFields and KeyFields.

dsoDynamicSQLDeleteEh

the record deletion operation will be generated dynamically based on the filled in UpdateTable and KeyFields properties.

The DynaSQLParams.KeyFields property specifies the key field of the record. It will be used to form a WHERE clause when deleting or updating a record. The DynaSQLParams.UpdateFields property specifies all fields that will be used to form the UpdateSQL and InsertSQL expression. The DynaSQLParams.UpdateTable property specifies the name of the updated table.

The SkipUnchangedFields property specifies that fields that have not changed are not added to the SQL UpdateSQL expression.

This is useful when the table contains many fields and only a few fields have changed.