Never use “ _id“ that is a name based on location and tell you this is probably not a real key at all. That is why things like “ _category_id” or “ _type_id” are garbage names. A look-up table deals with attributes and their values, not entities, so by definition, this is not used in such tables.
The attribute properties that deal with encodings for scales are the candidates for look-up tables. Some properties do not apply to some attributes - “ employee_diameter” is not something we need to model just yet and “ employee_species” is a bit insulting. The example used in the base document was an attribute of “tree” with properties like “ tree_diameter“, “ tree_species” and so forth. The ISO-11179 data element-naming conventions have the format _. That is, you are likely to see a table which translates an encoding into a description that a human being can understand. Most of the time, they are used for display purposes rather than computations. The concept of pre-calculating a function and storing the outputs can be carried over to databases. Today, you can get a more powerful calculator on a spike card in the check-out line of a school bookstore. These machines marked the end of look-up tables in textbooks. The price of that model dropped to less than one payment before I paid it off. I still remember my first Casio scientific calculator that I bought with my Playboy Club Key account in 12 monthly installments. Look up tables were easy for anyone to use and usually went to five decimal places. There were no cheap calculators and slide rulers were good to only three decimal places and required some skill to use. Trigonometry books had sines, cosines, tangents and maybe haversines and spherical trig functions. Finance books had compound interest, net present value (NPV) and internal rate of return (IIR). If you can find an old text book (1960’s or earlier), there is a good chance you will find look-up tables in the back. Auxiliary tables hold static data for use in the system, acting as the relational replacement for computations.
Staging tables bring in “dirty data” so we can scrub it and then insert it into base tables. Slightly outside of the tables in the data model, we have other kinds of tables.
Tables, in a properly designed schema, model either an entity or a relationship, but not both. Look-up Tables in SQL - Simple Talk Skip to content
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