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  2. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    Title Authors ----- ----- SQL Examples and Guide 4 The Joy of SQL 1 An Introduction to SQL 2 Pitfalls of SQL 1 Under the precondition that isbn is the only common column name of the two tables and that a column named title only exists in the Book table, one could re-write the query above in the following form:

  3. Day count convention - Wikipedia

    en.wikipedia.org/wiki/Day_count_convention

    This convention accounts for days in the period based on the portion in a leap year and the portion in a non-leap year. The days in the numerators are calculated on a Julian day difference basis. In this convention the first day of the period is included and the last day is excluded. The CouponFactor uses the same formula, replacing Date2 by Date3.

  4. Calendar date - Wikipedia

    en.wikipedia.org/wiki/Calendar_date

    A calendar date is a reference to a particular day represented within a calendar system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "25 January 2025" is ten days after "15 January 2025". The date of a particular event depends on the observed time zone.

  5. 360-day calendar - Wikipedia

    en.wikipedia.org/wiki/360-day_calendar

    The 360-day calendar is a method of measuring durations used in financial markets, in computer models, in ancient literature, and in prophetic literary genres.. It is based on merging the three major calendar systems into one complex clock [citation needed], with the 360-day year derived from the average year of the lunar and the solar: (365.2425 (solar) + 354.3829 (lunar))/2 = 719.6254/2 ...

  6. Doomsday rule - Wikipedia

    en.wikipedia.org/wiki/Doomsday_rule

    The doomsday's anchor day calculation is effectively calculating the number of days between any given date in the base year and the same date in the current year, then taking the remainder modulo 7. When both dates come after the leap day (if any), the difference is just 365y + ⁠ y / 4 ⁠ (rounded down). But 365 equals 52 × 7 + 1, so after ...

  7. Determination of the day of the week - Wikipedia

    en.wikipedia.org/wiki/Determination_of_the_day...

    For example, September and December correspond, because 1 September falls on the same day as 1 December (as there are precisely thirteen 7-day weeks between the two dates). Months can only correspond if the number of days between their first days is divisible by 7, or in other words, if their first days are a whole number of weeks apart.

  8. Zeller's congruence - Wikipedia

    en.wikipedia.org/wiki/Zeller's_congruence

    represents the progression of the day of the week based on the year. Assuming that each year is 365 days long, the same date on each succeeding year will be offset by a value of =. Since there are 366 days in each leap year, this needs to be accounted for by adding another day to the day of the week offset value.

  9. SQL - Wikipedia

    en.wikipedia.org/wiki/SQL

    SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...