Variables, Parameters, and Expressions
In order to create modular and robust solutions, developers will often create variables and routines to access those variables. Integration Services is no different in this regard. The variables available to SSIS have their own data types that often correlate to SQL Server data types. Parameters are used to pass values between parent and child packages to extend the modularity of an ETL project. And an expression language is provided to allow the ETL process to read or modify the values of both during runtime. The expression language can certainly get convoluted, so it is recommended that you take Churchill’s words to heart and keep the logic minimal, readable, and easily modifiable.
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