I have the following query:
ALTER TABLE ROUTE ADD FOREIGN KEY (RID) REFERENCES RESERVATION(RID) ON DELETE CASCADE
but it generates me an error:
#1452 - Cannot add or update a child row: a foreign key constraint fails (`SmarTrek`.`#sql-91e_d09`, CONSTRAINT `FK_RID` FOREIGN KEY (`RID`) REFERENCES `RESERVATION` (`RID`) ON DELETE CASCADE)
In designer mode, here's what it looks like:
That would meant that you already have data in the ROUTE table that does not satisfy the foreign key constraint.
To find the offending records, so you can update them to some other value (that exists), you can use
select *
from route
where rid not in (select rid from reservation)
THERE may b 2 reasons
ROUTE
TABLE which have RID
that does not exist in RESERVATION(RID)
ROUTE (RID)
& RESERVATION(RID)
both should be same ( unsigned/signed)
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