In addition to FileMaker's ODBC/JDBC guide (referenced by Ronnie), you might want to take some time to review the following references on SQL data types:
There is no such thing as a global field in any SQL database. Also, be aware that the field types that FileMaker shows you via ODBC or ESS do not provide you with all the detail you would normally get if you were using a native SQL table viewer/editor (such as PHPmyAdmin).
Technically, MySQL treats BLOBs as a text data-type. I'm not certain you can load data into a BLOB field using either ESS or ODBC - you may need to use something like ScriptMaster to put it into Base-64 format first. If you do that, however, I'm not sure you need to set-up the field in MySQL as a BLOB. Since Base-64 is just text, you could hypothetically store it as text and decode it when necessary.
I hope that helps.
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