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manual.texi minor change log fixes
manual.texi fix age calculations in the tutorial section to manual.texi determine age in integer years and to account for manual.texi relative order of dates within calendar year.
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paul@central.snake.net
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1 changed files with 85 additions and 69 deletions
154
Docs/manual.texi
154
Docs/manual.texi
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@ -13170,75 +13170,89 @@ MySQL provides several functions that you can use to perform
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calculations on dates, for example, to calculate ages or extract
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parts of dates.
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To determine how many years old each of your pets is, compute age as the
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difference between the birth date and the current date. Do this by
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converting the two dates to days, take the difference, and divide by 365 (the
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number of days in a year):
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To determine how many years old each of your pets is, compute the
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difference in the year part of the current date and the birth date, then
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subtract one if the current date occurs earlier in the calendar year than
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the birth date. The following query shows, for each pet, the birth date,
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the current date, and the age in years.
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@example
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mysql> SELECT name, (TO_DAYS(NOW())-TO_DAYS(birth))/365 FROM pet;
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+----------+-------------------------------------+
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| name | (TO_DAYS(NOW())-TO_DAYS(birth))/365 |
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+----------+-------------------------------------+
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| Fluffy | 6.15 |
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| Claws | 5.04 |
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| Buffy | 9.88 |
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| Fang | 8.59 |
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| Bowser | 9.58 |
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| Chirpy | 0.55 |
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| Whistler | 1.30 |
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| Slim | 2.92 |
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| Puffball | 0.00 |
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+----------+-------------------------------------+
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mysql> SELECT name, birth, CURRENT_DATE,
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-> (YEAR(CURRENT_DATE)-YEAR(birth))
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-> - (RIGHT(CURRENT_DATE,5)<RIGHT(birth,5))
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-> AS age
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-> FROM pet;
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+----------+------------+--------------+------+
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| name | birth | CURRENT_DATE | age |
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+----------+------------+--------------+------+
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| Fluffy | 1993-02-04 | 2001-08-29 | 8 |
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| Claws | 1994-03-17 | 2001-08-29 | 7 |
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| Buffy | 1989-05-13 | 2001-08-29 | 12 |
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| Fang | 1990-08-27 | 2001-08-29 | 11 |
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| Bowser | 1989-08-31 | 2001-08-29 | 11 |
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| Chirpy | 1998-09-11 | 2001-08-29 | 2 |
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| Whistler | 1997-12-09 | 2001-08-29 | 3 |
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| Slim | 1996-04-29 | 2001-08-29 | 5 |
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| Puffball | 1999-03-30 | 2001-08-29 | 2 |
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+----------+------------+--------------+------+
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@end example
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Although the query works, there are some things about it that could be
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improved. First, the result could be scanned more easily if the rows were
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presented in some order. Second, the heading for the age column isn't very
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Here, @code{YEAR()} pulls out the year part of a date and @code{RIGHT()}
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pulls off the rightmost five characters that represent the @code{MM-DD}
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(calendar year) part of the date. The part of the expression that
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compares the @code{MM-DD} values evaluates to 1 or 0, which adjusts the
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year difference down a year if @code{CURRENT_DATE} occurs earlier in
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the year than @code{birth}. The full expression is somewhat ungainly,
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so an alias (@code{age}) is used to make the output column label more
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meaningful.
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The first problem can be handled by adding an @code{ORDER BY name} clause to
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sort the output by name. To deal with the column heading, provide a name for
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the column so that a different label appears in the output (this is called a
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column alias):
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The query works, but the result could be scanned more easily if the rows
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were presented in some order. This can be done by adding an @code{ORDER
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BY name} clause to sort the output by name:
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@example
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mysql> SELECT name, (TO_DAYS(NOW())-TO_DAYS(birth))/365 AS age
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mysql> SELECT name, birth, CURRENT_DATE,
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-> (YEAR(CURRENT_DATE)-YEAR(birth))
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-> - (RIGHT(CURRENT_DATE,5)<RIGHT(birth,5))
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-> AS age
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-> FROM pet ORDER BY name;
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+----------+------+
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| name | age |
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+----------+------+
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| Bowser | 9.58 |
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| Buffy | 9.88 |
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| Chirpy | 0.55 |
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| Claws | 5.04 |
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| Fang | 8.59 |
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| Fluffy | 6.15 |
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| Puffball | 0.00 |
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| Slim | 2.92 |
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| Whistler | 1.30 |
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+----------+------+
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+----------+------------+--------------+------+
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| name | birth | CURRENT_DATE | age |
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+----------+------------+--------------+------+
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| Bowser | 1989-08-31 | 2001-08-29 | 11 |
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| Buffy | 1989-05-13 | 2001-08-29 | 12 |
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| Chirpy | 1998-09-11 | 2001-08-29 | 2 |
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| Claws | 1994-03-17 | 2001-08-29 | 7 |
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| Fang | 1990-08-27 | 2001-08-29 | 11 |
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| Fluffy | 1993-02-04 | 2001-08-29 | 8 |
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| Puffball | 1999-03-30 | 2001-08-29 | 2 |
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| Slim | 1996-04-29 | 2001-08-29 | 5 |
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| Whistler | 1997-12-09 | 2001-08-29 | 3 |
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+----------+------------+--------------+------+
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@end example
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To sort the output by @code{age} rather than @code{name}, just use a
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different @code{ORDER BY} clause:
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@example
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mysql> SELECT name, (TO_DAYS(NOW())-TO_DAYS(birth))/365 AS age
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-> FROM pet ORDER BY age;
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+----------+------+
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| name | age |
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+----------+------+
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| Puffball | 0.00 |
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| Chirpy | 0.55 |
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| Whistler | 1.30 |
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| Slim | 2.92 |
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| Claws | 5.04 |
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| Fluffy | 6.15 |
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| Fang | 8.59 |
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| Bowser | 9.58 |
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| Buffy | 9.88 |
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+----------+------+
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mysql> SELECT name, birth, CURRENT_DATE,
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-> (YEAR(CURRENT_DATE)-YEAR(birth))
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-> - (RIGHT(CURRENT_DATE,5)<RIGHT(birth,5))
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-> AS age
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-> FROM pet ORDER BY age;
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+----------+------------+--------------+------+
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| name | birth | CURRENT_DATE | age |
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+----------+------------+--------------+------+
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| Chirpy | 1998-09-11 | 2001-08-29 | 2 |
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| Puffball | 1999-03-30 | 2001-08-29 | 2 |
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| Whistler | 1997-12-09 | 2001-08-29 | 3 |
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| Slim | 1996-04-29 | 2001-08-29 | 5 |
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| Claws | 1994-03-17 | 2001-08-29 | 7 |
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| Fluffy | 1993-02-04 | 2001-08-29 | 8 |
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| Fang | 1990-08-27 | 2001-08-29 | 11 |
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| Bowser | 1989-08-31 | 2001-08-29 | 11 |
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| Buffy | 1989-05-13 | 2001-08-29 | 12 |
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+----------+------------+--------------+------+
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@end example
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A similar query can be used to determine age at death for animals that have
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@ -13248,12 +13262,14 @@ values, compute the difference between the @code{death} and @code{birth}
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values:
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@example
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mysql> SELECT name, birth, death, (TO_DAYS(death)-TO_DAYS(birth))/365 AS age
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-> FROM pet WHERE death IS NOT NULL ORDER BY age;
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mysql> SELECT name, birth, death,
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-> (YEAR(death)-YEAR(birth)) - (RIGHT(death,5)<RIGHT(birth,5))
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-> AS age
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-> FROM pet WHERE death IS NOT NULL ORDER BY age;
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+--------+------------+------------+------+
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| name | birth | death | age |
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+--------+------------+------------+------+
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| Bowser | 1989-08-31 | 1995-07-29 | 5.91 |
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| Bowser | 1989-08-31 | 1995-07-29 | 5 |
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+--------+------------+------------+------+
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@end example
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@ -13328,7 +13344,7 @@ mysql> SELECT name, birth FROM pet
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Note that @code{MONTH} returns a number between 1 and 12. And
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@code{MOD(something,12)} returns a number between 0 and 11. So the
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addition has to be after the @code{MOD()} otherwise we would go from
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addition has to be after the @code{MOD()}, otherwise we would go from
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November (11) to January (1).
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@ -46696,35 +46712,35 @@ not yet 100% confident in this code.
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@appendixsubsec Changes in release 3.23.42
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@itemize @bullet
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@item
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Enforce that all tables in a @code{MERGE} table comes from the same
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Enforce that all tables in a @code{MERGE} table come from the same
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database.
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@item
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Fixed bug with @code{LOAD DATA INFILE} and transactional tables.
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@item
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Fix bug when using @code{INSERT DELAYED} with wrong column definition.
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@item
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Fixed coredump during REPAIR of some particulary broken tables.
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Fixed coredump during @code{REPAIR} of some particularly broken tables.
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@item
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Fixed bug in @code{InnoDB} and @code{AUTO_INCREMENT} columns.
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@item
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Fixed critical bug in @code{InnoDB} and @code{BLOB}'s. If one has used
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@code{BLOB}'s larger than 8K in an @code{InnoDB} table one must dump
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the table with @code{mysqldump}, drop it and restore it from the dump.
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Fixed critical bug in @code{InnoDB} and @code{BLOB} columns. If one has
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used @code{BLOB} columns larger than 8K in an @code{InnoDB} table, one must
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dump the table with @code{mysqldump}, drop it and restore it from the dump.
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@item
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Applied large patch for OS/2 from Yuri Dario.
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@item
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Fixed problem with InnoDB when one could get the error @code{Can't
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Fixed problem with @code{InnoDB} when one could get the error @code{Can't
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execute the given command...} even when one didn't have an active
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transaction.
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@item
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Applied some minor fixes that concerns Gemini.
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Applied some minor fixes that concern Gemini.
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@item
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Use real arithmetic operations even in integer context if not
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all arguments are integers. (Fixes uncommon bug in some integer
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context).
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contexts).
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@item
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Don't force everything to lower cases on windows. (To fix problem
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with windows and @code{ALTER TABLE}). Now @code{--lower_case_names}
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Don't force everything to lower cases on Windows. (To fix problem
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with Windows and @code{ALTER TABLE}). Now @code{--lower_case_names}
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also works on Unix.
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@item
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Fixed that automatic rollback that is done when thread end doesn't lock
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@ -46740,7 +46756,7 @@ Added option @code{--sql-mode=option[,option[,option]]}.
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@xref{Command-line options}.
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@item
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Fixed possible problem with @code{shutdown} on Solaris where the
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@code{.pid} file wasn't deleted.
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@file{.pid} file wasn't deleted.
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@item
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InnoDB now supports < 4 GB rows. The former limit was 8000 bytes.
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@item
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