I recently met an annoying issue when reading Excel data in SSIS. The issue was when a column contained a mix of data-types – in this case string and numeric information. The problem comes from the fact that Excel does not have a concept of column data-types, and the issues in SSIS come from the way the OLE-DB provider for Excel attempts to resolve this.
I found the information I needed in an excellent blog post here, and I won’t repeat the content here. One additional point that is specific to SSIS is how to add the IMEX extended property to the connection string. In Visual Studio 2005 (I’ve not checked other versions) you can only do this by editing the ConnectionString property directly in the Properties window – the dialog box doesn’t offer this option. See the image below.