1. PART Evaluation and optimization: A schema of the ski shop information system is given: Customer (cid, name, surname, address, telephone); Employee (eid, name, surname, address, telephone); Purchase (pid, sid, cid, eid, date); Skiis (sid, brand, model, length, hardness) Additional information is given: | Customer] =150 pages, 40 records/page | Employee | = 2 pages, 40 records/page | Purchase | = 2000 pages, 100 records/page | Skiis | = 250 pages, 30 records/page Buffer can store up to 2500 pages. Let's assume that the following indices are now set on the schema from the previous task: Level 2 B+ index on the attribute Purchase.date Hash index on the attribute Skiis.sid - Our DBMS has the following algorithms to perform the join: - Hash join - Index nested loops join - Sort-merge join Translate the following SQL query into relational algebra and find the plan that reads the fewest pages or blocks: SELECT Skiis.model, Skiis.length FROM Skiis JOIN Purchase ON (Skiis.sid = Purchase.sid) WHERE Skiis.brand = 'Elan' AND Purchase.date > '31.12.2023'

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Fundamentals of Datawarehouse

A data warehouse is a data repository which is used to store large quantities of historical data that are mostly used for creating reports that help businesses to identify their weaknesses and strengths. For example, demographics data about people of a region can help businesses identify the needs and preferences of the region’s population. A data warehouse acts as a central storage for storing data that comes from one or more heterogenous sources. It also consists of data which can be old and of historical value. One of the most important applications of this type of system is that it is used for supporting business intelligence and data analytics applications.