Chapter 7

Handling Temporal Data

IN THIS CHAPTER

Bullet Defining times and periods

Bullet Tracking what happened at specific times

Bullet Providing an audit trail of changes to the data

Bullet Handling both what happened and when the event was recorded

Bullet Formatting and parsing dates and times

Before SQL:2011, ISO/IEC standard SQL had no mechanism for dealing with data that was valid at one point in time but not valid at another. Any application that requires that an audit trail be kept needs that capability. This means that the burden of keeping track of what was true at a given time falls on the application programmer rather than the database. This sounds like a recipe for complicated, over-budget, late, and bug-infested applications.

Syntax was added to SQL:2011 that enables handling of temporal data without messing up the way code for non-temporal data is handled. This is a big advantage for anyone who wants to add temporal capability to an existing SQL database. Even though SQL:2011 standardized how to handle ...

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