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Display Width Clarification (numeric data types)
Posted by: Jeff Miner
Date: August 14, 2009 10:49AM

The certification book explains numeric data types in regards to display width: "The display width indicating the maximum number of characters to use when presenting column values in a query output." (p.61) Then, it goes on to say "When you SELECT the column in a query, mysql displays the entire value..., not just the the first four digits of the value." (p. 62)

This sort of information doesn't really help a lot.

Altogether, I've looked through the reference manual and certification study guide book, but with such contradictions and no explanation, I can't determine what display width actually does.

This is the best I can piece together with the information I can find:
1. Display width doesn't change storage requirements for the data type.
2. Display width doesn't alter the actual data in any way (ie: it stores the entire value for the data)
3. A column returns it's full value when called in a query, regardless of the display width (the book directly contradicts this claim it makes as seen above)

Are these statements true? If so, how do I SEE the values "hidden" by using a display width? Will the full values show up in a query (like the book states) or will they not (like the book states)? Does your query have to have a SELECT statement for the full value to be returned?

Is there something I am missing? I really don't see any reason to set a display width for integers with the explanations I have of them now. What benefit does setting a display width have?

Edited 1 time(s). Last edit at 08/14/2009 10:50AM by Jeff Miner.

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Display Width Clarification (numeric data types)
August 14, 2009 10:49AM

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