XPro User Group News (Con’t from page 9)

different from the .MDX/CDX (not to mention .NDX) format. The .DB’s use a primary key index that, if used, must

be unique. Also available are secondary indexes (which first require the primary index) that not only allow for

another view of the table like .MDXICDX’s, but are necessary for an Referential Integrity links. In any case, the

primary index (key) is always in effect, meaning that it can’t have duplicate values no matter which secondary

index you may be using to view your data. I should also mention that the primary key actually the order of

table, which is something you almost never do with a .DBF. This can create an effect called flyaway, when an

edited record suddenly disappears from view in a table as it’s automatically sorted to the proper position. (This

was very disorienting to me the first time it happened, being used to dBASE III+ and .NDX indexes.) The final

comment about indexes worth mentioning here is that you won’t have access to some of the .MDX/CDX indexing

functions or operators with the .DB tables, nor will you be able to use descending indexes like you may be used

to.

To be continued...

[Ed. Note: Randy’s article continues with a history of xBase, including the involvement of Borland and the tech-

nology that was acquired with the purchase of Arago. It is of enough significance to warrant a separate column.

However, due to space limitations in this month’s newsletter, we will be printing it in its entirety in next month’s

newsletter.)

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