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Constraints enables business rules to be enforced by the database instead of via application code. Through the judicious use of constraints, application and SQL coding can be minimized and data integrity can be maximized. Constraints may be applied to columns in the form of uniqueness requirements, relational integrity constraints to other tables/rows, allowable values and data types.For example, a column containing a product price should probably only accept positive values. But there is no standard data type that accepts only positive numbers. Another issue is that you might want to constrain column data with respect to other columns or rows. For example, in a table containing product information, there should be only one row for each product number. (more…)
Previously i posted a very useful class to categorize multi-dimensional array. I wrote another one that is just an alternative for array_unique function.
This extension notifies you with latest London underground tube updates. You can click on the browser button and check the status of any tube line.By default the extension updates the status in every 5 mins.
In the second example I am going to use Standard PHP Library (SPL) to notify all attendees about the party location change. SPL has 2 interfaces and a Class for Observer.
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Gaurav Jassal
