mysql - ""Duplicate Entry" while inserting in a Composite primary keyed table - 


create table if not exists `mytable` ( `machine_no` varchar(50) character set ascii not null, `date` datetime not null, `nature` int(11) default null, `start` time not null, primary key (`machine_no`,`date`), unique key `date` (`date`), unique key `start` (`start`), unique key `start_2` (`start`), unique key `nature` (`nature`) ) engine=innodb default charset=latin1;

this table has composite key.

when try insert 2 records same date/time different value of machine_no. says duplicate entry date. dont understand reason it. composite key, should duplicate entry in both attributes.

your primary key works fine:

primary key (`machine_no`,`date`),

what causes issue unique key have:

unique key `date` (`date`),

this not allow 2 rows same datetime inserted.

similarly other 3 unique keys cause torubles well:

unique key `start` (`start`), unique key `start_2` (`start`), unique key `nature` (`nature`)

so, make keys simple (not unique).

and there no reason have 2 identical keys differ in name (start , start_2)


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