Chasing polarized order dependencies – semantic scholar o review database
Dependencies have played a significant role in database design for many years. Database user interface They have also been shown to be useful in query optimization. Database usa reviews In this paper, we discuss the new type of dependency for polarized lexicograph-ically ordered sets of tuples. Hollywood u database We introduce formally the concept of polarized order dependencies (PODs). Uottawa database We discuss their potential significance for database systems, and present a chase procedure for testing logical implication for them. Yorku database 1 Introduction Consider the following SQL query in Example 1. Database view In the schema, Dates is a dimension table with a row per day, and Sales is a large fact table recording all individual sales. Database vs spreadsheet The column date_id is the primary key for Dates, each row describes a given day with explicit columns as year, quarter, month, and day that describe the natural date values.
Database version control Of course, quarter is logically redundant in the group by, as month (which follows it in the group by) functionally determines quarter. Database viewer (First quarter encompasses the months of January, February, and March, second quarter, the months of April, May, and June, and so forth.) The query’s author could not leave quarter out of the group by, because it is stated in the select. Database visualization The query optimizer could, however, remove quarter to accomplish the group by on year, quarter, month, sales if it recognizes that year, month and year, quarter, month offer the same partition. Database vault This is done by query optimizers today – given the functional dependency (FD) information that month → quarter is available to the optimizer – by rewrite . Database virtualization For the query above, the rewrite might still not be applied, however since the query also specifies the answers to be ordered by year asc, quarter asc, month 168 asc, sales desc. Database vs server The FD that month → quarter is not logically sufficient to eliminate quarter from the order by, as it was to eliminate it from the group by. Database versioning To see that the functional dependency does not suffice to eliminate quarter from the order by, imagine the values for quarter were the strings first, second, third, and fourth. Database vendors Data would be lexicographically ordered as first, fourth, second, then third! Of course, we intend that values of quarter are, say, 1, 2, 3, and 4, so the data would order naturally as by date. V database in oracle It is unfortunate, then, that quarter is, in fact, redundant (in this query) in the order by also, but that the optimizer does … Extracted Key Phrases