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Universal database vs eav modeling5/11/2023 The “values” are the quantity purchased and total line item price.No competent database designer would hard-code individual products such as Doritos or Diet Coke as columns in a table.) (Products are just as volatile as clinical findings, possibly even more so: new products are introduced every month, while others are taken off the market if consumer acceptance is poor. The “attribute” is a foreign key into a products table, from where one looks up description, unit price, discounts and promotions, etc.This is used to tag each line item internally, though on the receipt the information about the Sale appears at the top (shop location, sale date/time) and at the bottom (total value of sale). The “entity” is the sale/transaction id - a foreign key into a sales transaction table.Like the clinical findings for a given patient, the sales receipt is sparse. The receipt lists only details of the items actually purchased, instead of listing every product in the shop that the customer might have purchased but didn’t. The EAV data described above is comparable to the contents of a supermarket sales receipt (which would be reflected in a Sales Line Items table in a database). The example below illustrates symptoms findings that might be seen in a patient with COVID-19. This would depend on the data type, and we discuss how values are stored shortly. At the very least, the attribute definitions table would contain the following columns: an attribute ID, attribute name, description, data type, units of measurement, and columns assisting input validation, e.g., maximum string length and regular expression, maximum and minimum permissible values, set of permissible values, etc.
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