An occasional chance, and reducing data to manageable levels
Archive - Originally posted on "The Horse's Mouth" - 2005-12-04 10:35:57 - Graham Ellis
If there's a 1 in 5 (20%) chance of it being a dry day at the moment, a 20% chance of it not being freezing cold, and a 20% chance of me having a day that I'm not training or otherwise involved, then it follows (since the conditions aren't related) that there's just a 1 in 125 or less that 1% chance of all three co-inciding. A.k.a. "fat chance".
Which is why you would have found me and Lisa, yesterday, re-roofing the conservatory / store room in which newsletters, envelopes, cables and 101 other business supplies are kept. The plastic sheeting on the roof of this '60s addition to our place was - to put it mildly - life expired and there was a real danger of some of the things kept in there getting damaged so we simply couldn't wait for a co-incidence of three 1-in-5s. "Between showers" is, I think, the best way to describe what we did; it was a darned sight dryer that the last few days which have lead, once again, to the formation of Lake Melksham.
Interestingly, SQL SELECT commands also use this principle of "a proportion of a proportion is a tiny bit of data" to reduce the amount of information supplied back to the using application by a database. In a select command, you specify which columns you want, and you also specify which rows you want. Which leads to a rapid data reduction. For example, if you have a 10 Mbyte database table and you select just 4 columns out of 20, and then just 100 rows out of 10000, your result set will be just 20k.
Which is why you would have found me and Lisa, yesterday, re-roofing the conservatory / store room in which newsletters, envelopes, cables and 101 other business supplies are kept. The plastic sheeting on the roof of this '60s addition to our place was - to put it mildly - life expired and there was a real danger of some of the things kept in there getting damaged so we simply couldn't wait for a co-incidence of three 1-in-5s. "Between showers" is, I think, the best way to describe what we did; it was a darned sight dryer that the last few days which have lead, once again, to the formation of Lake Melksham.