Acronym it. This has become such a problem that it is even evaluated at the level of medical academies such as the American Academy of Dermatology. Acronyms are often taught as mnemonic devices, for example in physics the colors of the visible spectrum are said to be "ROY G. BIV" ("red-orange-yellow-green-blue-indigo-violet"). They are also used as mental checklists, for example in aviation: "GUMPS", which is "Gas-Undercarriage-Mixture-Propeller-Seatbelts". Other examples of mnemonic acronyms are "CAN SLIM", and "PAVPANIC" as well as "PEMDAS". It is not uncommon for acronyms to be cited in a kind of false etymology, called a "folk etymology", for a
Query optimization SQL query. There are two types of optimization. These consist of logical optimization—which generates a sequence of relational algebra to solve the query—and physical optimization—which is used to determine the means of carrying out each operation. Most query optimizers represent query plans as a tree of "plan nodes". A plan node encapsulates a single operation that is required to execute the query. The nodes are arranged as a tree, in which intermediate results flow from the bottom of the tree to the top. Each node has zero or more child nodes—those are nodes whose output is fed as input to