field: Fields describe a single aspect of each member of a table. A student record, for instance, might contain a last name field, a first name field, a date of birth field and so on. All records have exactly the same structure, so they contain the same fields.
Many jurisdictions require one or more bicycle lights to be fitted to bicycles ridden at night â generally a white light in the front and a red light at the back.
A 3 W halogen dynamo headlight will light the road up about the same as a rechargeable light of around 7â10 W, but the rechargeable usually outputs much more light to the sides, which is useful on trails (although wide and narrow beam versions are available).n Germany, it was illegal to use bicycles without a dynamo-based lighting system except on racing bicycles below 11 kg. This stimulated the market in Germany for high quality dynamos. Since 5 July 2013, a change in the law allows use of battery-powered lights.