{"product_id":"9783540549192","title":"Lecture Notes in Computer Science","description":"\u003ch1\u003eLecture Notes in Computer Science\u003c\/h1\u003e \u003ch2\u003eGrahne, Gösta\u003c\/h2\u003e \u003cp\u003eIn a relational database the information is recorded as rows\nin tables.     However, in many practical situations the\navailable information is          incomplete and the values for some\ncolumns are missing. Yet few existing    database management\nsystems allow the user to enter null values in the      database.\nThis monograph analyses the problems raised by allowing           null\nvalues in relational databases. The analysis covers\nsemantical,    syntactical, and computational aspects.\nAlgorithms for query evaluation,    dependency enforcement and\nupdates in the presence of null values are also  given.\nThe analysis of the computational complexity of the\nalgorithms   suggests that from a practical point of view the\ndatabase should be stored  as Horn tables, which are\ngeneralizations of ordinary relations, allowing   null values\nand Horn clause-like restrictions on these null values.         Horn\ntables efficiently support a large class of queries,\ndependencies  and updates.\u003c\/p\u003e \u003ch3\u003eDetails\u003c\/h3\u003e \u003cp\u003ePublished by: Springer\u003c\/p\u003e \u003cp\u003ePublication Date: 1991-11-13\u003c\/p\u003e \u003cp\u003eFormat: Paperback\u003c\/p\u003e \u003cp\u003eISBN-13: 9783540549192\u003c\/p\u003e \u003cp\u003eDOI: 10.1007\/3-540-54919-6\u003c\/p\u003e \u003cp\u003eDimensions: 235cm x155cm\u003c\/p\u003e \u003cp\u003ePages: 164\u003c\/p\u003e ","brand":"Springer Berlin Heidelberg","offers":[{"title":"Default Title","offer_id":45369862062220,"sku":"9783540549192","price":49.49,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0710\/9545\/1788\/files\/9783540549192.jpg?v=1773966034","url":"https:\/\/fh90cf-fv.myshopify.com\/products\/9783540549192","provider":"Late Knight Books and Services, LLC","version":"1.0","type":"link"}