The File Column (BLOBs)

Many database servers allow you to store Binary Large Objects (BLOBs) or Character Large Objects (CLOBs) in a table column. Logi Info developers can manipulate this kind of data using the File Column element.

The following topics discuss the File Column element:

• Preparing Data in a Datalayer
• Working with Retrieved Data
• Example: Retrieving Dashboard Configuration Data

About BLOBs and CLOBs

The ability of some database servers to store large amounts of data in individual table columns provides a interesting challenge for data storage and retrieval. A common BLOB implementation example is an HR table that stores employee data and includes an actual photo of each employee in one of its columns. Other examples of BLOBs include audio and multimedia objects, and even executable code.

Other implementations may store large amounts of text, called CLOBs, in the same manner. For example, the HTML for entire web pages could be stored in a single table column as part of a content management system. Other examples of CLOBs include XML data, documents, and logs.

BLOB and CLOB data may be stored as a collection of bytes right in the database's standard storage area or they may reside outside it, in auxiliary files, referenced by pointers in the table column record. The size of a BLOB or CLOB can be quite large; for example, ODBC and JDBC specs allow up to 4GB of data.

Let's see how this kind of data can be retrieved for use in a Logi application.