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ADDTIME(expr1,expr2) is a hybrid function.
- In case when expr1 is DATETIME, the result type is DATETIME.
- In case when expr1 is TIME, the result type is TIME.
- Otherwise, the result type is VARCHAR, and the choice between
DATETIME or TIME format is done per-row.
In case of VARCHAR result, the function must follow the standard
MySQL/MariaDB convention:
character set and collation of a string function returning a result
from numeric or temporal input should be set according to
@@character_set_connection and @@collation_connection
respectively.
http://dev.mysql.com/doc/refman/5.6/en/type-conversion.html
In MySQL 5.6, implicit conversion of a numeric or temporal value to string produces a value that has a character set and collation determined by the character_set_connection and collation_connection system variables.
Consider this SQL script:
set character_set_connection=ucs2;
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select charset(addtime(_latin1'10:01:01',_latin1'10:00:00'));
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drop table if exists t1;
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create table t1 as select addtime(_latin1'10:01:01',_latin1'10:00:00') as a;
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show create table t1;
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MySQL-5.6 does follow this rule, and the output is:
+-------------------------------------------------------+
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| charset(addtime(_latin1'10:01:01',_latin1'10:00:00')) |
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+-------------------------------------------------------+
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| ucs2 |
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+-------------------------------------------------------+
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1
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+-------+--------------------------------------------------------------------------------------------
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...
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------------------+
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| Table | Create Table |
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+-------+--------------------------------------------------------------------------------------------------------------+
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| t1 | CREATE TABLE `t1` (
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`a` varchar(29) CHARACTER SET ucs2 DEFAULT NULL
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) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
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+-------+--------------------------------------------------------------------------------------------------------------+
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Notice: ucs2 is consistently reported in both tables in the output.
MariaDB does not follow this rule, and the output is:
+-------------------------------------------------------+
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| charset(addtime(_latin1'10:01:01',_latin1'10:00:00')) |
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+-------------------------------------------------------+
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| binary |
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+-------------------------------------------------------+
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...
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+-------+-------------------------------------------------------------------------------------------+
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| Table | Create Table |
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+-------+-------------------------------------------------------------------------------------------+
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| t1 | CREATE TABLE `t1` (
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`a` varchar(26) DEFAULT NULL
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) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
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+-------+-------------------------------------------------------------------------------------------
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Moreover, the result of CHARSET() and of "SHOW CREATE" do not
match to each over (binary vs latin1).
The same problem is observed with another temporal hybrid function DATE_ADD.
The script:
set character_set_connection=ucs2;
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select charset(date_add(_latin1'10:01:01',interval 10 second));
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drop table if exists t1;
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create table t1 as select date_add(_latin1'10:01:01',interval 10 second) as a;
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show create table t1;
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Results from MySQL-5.6 are consistently correct:
+---------------------------------------------------------+
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| charset(date_add(_latin1'10:01:01',interval 10 second)) |
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+---------------------------------------------------------+
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| ucs2 |
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+---------------------------------------------------------+
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+-------+--------------------------------------------------------------------------------------------------------------+
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| Table | Create Table |
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+-------+--------------------------------------------------------------------------------------------------------------+
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| t1 | CREATE TABLE `t1` (
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`a` varchar(29) CHARACTER SET ucs2 DEFAULT NULL
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) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
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+-------+--------------------------------------------------------------------------------------------------------------+
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Result from MariaDB-10.0 are wrong and non-consistent:
+---------------------------------------------------------+
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| charset(date_add(_latin1'10:01:01',interval 10 second)) |
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+---------------------------------------------------------+
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| binary |
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+---------------------------------------------------------+
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+-------+-------------------------------------------------------------------------------------------+
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| Table | Create Table |
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+-------+-------------------------------------------------------------------------------------------+
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| t1 | CREATE TABLE `t1` (
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`a` varchar(26) DEFAULT NULL
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) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
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+-------+-------------------------------------------------------------------------------------------+
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