Encyclopedia of Database Systems

Living Edition
| Editors: Ling Liu, M. Tamer Özsu


Living reference work entry
DOI: https://doi.org/10.1007/978-1-4899-7993-3_469-2



Windows were introduced as part of SQL:1999 OLAP functions. For instance, given a sequence of bids, it is possible to use the following SQL:2003 statement to find the last 40 offers (the current offer and the previous 39) for item 0021:
  • SELECT itemID, avg(Offer)



  • WHERE ItemID = 0021

When BIDS is instead a data stream, the “ORDER BY TIME” clause becomes redundant, and clauses such as “FOLLOWING” are often not supported in continuous query languages. However, these languages still provide a “PARTITION BY” clause (or the more traditional “GROUP BY” clause), whereby a user can specify that the average of the last 40 offers must be computed for all items, not just item 0021. In addition to entailing powerful and flexible analytical queries on ordered sequences and time series, as in databases, windows on data streams play the key role of synopsesand...

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Recommended Reading

  1. 1.
    Li J, et al. Semantics and evaluation techniques for window aggregates in data streams. In: Proceedings ACM SIGMOD international conference on management of data. 2005, p. 311–22.Google Scholar
  2. 2.
    Maier D, Tucker PA, Garofalakis M. Filtering, punctuation, windows and synopses. In: Chaudhry N, Shaw K, Abdelguerfi M, editors. Stream data management, vol. 30. Dordrecht: Kluwer; 2005. p. 35–56.CrossRefGoogle Scholar
  3. 3.
    Bai Y, et al. A data stream language and system designed for power and extensibility. In: Proceedings of international conference on information and knowledge management. 2006. p. 337–46.Google Scholar
  4. 4.
    Ghanem T, et al. Incremental evaluation of sliding-window queries over data streams. IEEE Trans Knowl Data Eng. 2007;19(1):57–72.CrossRefGoogle Scholar

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© Springer Science+Business Media LLC 2017

Authors and Affiliations

  1. 1.University of California-Los AngelesLos AngelesUSA