July 2010
Intermediate to advanced
840 pages
16h 33m
English
Content preview from Joe Celko's SQL for Smarties, 3rd Edition
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29.6. Other Temporal Functions
Another common set of functions, which are not represented in standard SQL, deal with weeks. For example, Sybase’s SQL Anywhere (née WATCOM SQL) has a DOW(<date>) that returns a number between 1 and 7 to represent the day of the week (1 = Sunday, 2 = Monday, . . ., 7 = Saturday, following an ISO standard convention). You can also find functions that add or subtract weeks from a date given the number of the date within the year and so on. The function for finding the day of the week for a date is called Zeller’s algorithm:
CREATE FUNCTION Zeller (IN z_year INTEGER, IN z_month INTEGER, IN z_day INTEGER) RETURNS INTEGER LANGUAGE SQL DETERMINISTIC BEGIN DECLARE m INTEGER; DECLARE d INTEGER; DECLARE y INTEGER; SET y ...
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