SSIS Output Columns

Question

I do not quite understand the difference between Output Columns and External Columns in SSIS. I searched for explanations on the Internet, but I'm still unclear. For example, this blog entry: http://consultingblogs.emc.com/jamiethomson/archive/2006/05/23/SSIS_3A00_-The-difference-between-output-columns-and-external-columns.aspx and this question: http://social.msdn.microsoft.com/forums/en-US/sqlintegrationservices/thread/f5fa8785-46cc-44e1-9251-8503d2725523/ .

For example, if you have a SQL OLEDB source with this query:

SELECT ID, Name FROM Person 

Then the results are written to a text file. Then there is an output column and an external column for each. Some web pages say that external columns contain metadata. For example, if Name is VARCHAR (30) in an OLEDB SQL data source and it is VARCHAR (50) in a text file, then what are the values ​​for the output columns and external columns?

Can someone point me to an MSDN article that clearly explains the differences? This morning I searched for more than an hour.

Answer 1

I have not found the entire MSDN article about this, but I think this figure of this MSDN article clearly shows this.

In a common data source, there are external columns that store information about the data structure in the source and output columns, which store the structure of the information that it sends along the data path. It copies data from external columns to output columns. Data recipients have input columns that store data about the date structure that it receives from the data path and external columns that describe the structure at the destination. It copies data from input columns to external columns.

In your case, it should be:

 Source: External columns: Name Type Length Id DT_I4 0 Name DT_STR 30 Output columns: Name Type Length Id DT_I4 0 Name DT_STR 30 Destination: Input columns: Name Type Length Id DT_I4 0 Name DT_STR 30 External columns: Name Type Length Name DT_STR 50