1452 Cannot add or update a child row a foreign key constraint fails mysql phpmyadmin 2022
1452 Cannot add or update a child row a foreign key constraint fails mysql phpmyadmin 2022
1452 Cannot add or update a child row a foreign key constraint fails mysql phpmyadmin 2022
The MySQL ERROR 1452 happens when you try to execute a data manipulation query into a table that has one or more failing foreign key constraints. The cause of this error is the values you’re trying to put into the table are not available in the referencing (parent) table.
How do I fix foreign key constraint failure?
The error message itself showing there is a foreign key constraint error, which means you are deleting a parent table where the child table contains the Primary table identifier as a foreign key. To avoid this error, you need to delete child table records first and after that the parent table record.
Why Cannot add or update a child row?
The error comes when you are trying to add a row for which no matching row in in the other table. “Foreign key relationships involve a parent table that holds the central data values, and a child table with identical values pointing back to its parent. The FOREIGN KEY clause is specified in the child table.
Content
10.8 -> hello everybody welcome to our new video uh today
we want to fix this error which is a error number
18.08 -> 1452 is my mysql error so what i did i tried
to put i was trying to put a foreign key
30.08 -> on this table so i've created a subject id
which is 11 inch but now you can see here
36.88 -> when i go and i say i want to to
put a foreign key what it does uh
46 -> let me say subject id this is
something crazy sub object id
56.96 -> which is that get it there so we go here
and we take it and we say subject id
67.84 -> um what is that okay let me see yes then
we go here and we try to get the database
78.08 -> this database we're using then we come
and we look for the table we want to
85.44 -> to get its primary key to be our foreign key in
this table so we're trying to get that tbr subject
95.68 -> this one we got it so it gets it
automatically if i say on cascade
102.88 -> i want on delete if that it deleted that site
it can be deleted this side so if i want to
110.72 -> also edit that site to be edited that's this side
so when we try to save this we get into problems
120.8 -> if i say okay you can see i can see we get
into problems let's go and analyze our data
130 -> that we're going to see that it's a
0 0 0 0 here and in the table here
140.48 -> we want to make a foreign key let me
get you to that table appearance um
150.4 -> please come no the table is called subject
table um can't see it here but i'm gonna get it
162.56 -> subject subject i can't seem
to see it but i'm gonna see it
172.88 -> subject subject student subject subject
subject subjects tbo subject student well
182.24 -> i don't know if my eyes are not working well
but okay that shouldn't be a problem to us
189.36 -> what we're gonna do we're going to try to go back
yeah and we'll try to say subject we say to say go
208.08 -> if there is no table like that is fine
um we're going to get tbl subject subject
222.16 -> uh we see if we can get that yes we got that
so after getting that subject you can see
229.44 -> in the subject id there is no id called
zero that could cause a little problem
236.96 -> also but in the foreign key there we can see
there's a subject called zero so now here
243.36 -> uh what i could do let me try to go also see the
structure of this table and you can see the phones
249.92 -> be nine nine or two okay everything's fine here
but we might be facing a problem that they were
255.44 -> trying to create a foreign key but there is no id
like this id so that id0 is not here that's why
263.2 -> uh we might be have facing that problem so i'm
gonna look for that table again then i try to
269.12 -> do something simple and see if we can can be fixed
like that uh tbl lessons we go here now we see all
277.68 -> these guys we have we're gonna put one we're gonna
give it one and uh we give it a one also here
285.92 -> give it a one wow what's going on here it's
giving me trouble here okay we're gonna give
293.12 -> it one one one one uh lessons okay we edit
this also we put a one we edit the second
306.88 -> another one we call it a one and we
edit another one we give it a one
314.72 -> and we edit another one we give it a one and uh we
save okay no we we we have one also we have to do
328 -> okay one and we saved so now let's try to
see if we can give a foreign key to this
365.6 -> yes we got it okay let's save and see
371.2 -> yes it worked so the issue here is one you cannot
create a primary foreign key in a child table
379.2 -> when there is no data which is going to
be similar to the data in the first table
386.64 -> there simply means whatever
391.04 -> happens here whatever i do we have in the child
table must happen at what in the secondary table
396.48 -> which means the mother table so that's the reason
why we could not find but if you want to do
402.24 -> that it simply means this table should be new or
you should delete everything here all the data
408 -> here if we say let me browse you should delete
everything here that's we can be able to create
414.72 -> so that's why we had a zero it could not work
only we would it would have worked if the zeros
420.4 -> we could go and put a zero into that and also
you saw the cascading stuff whereby if we go to
431.36 -> our our table and change if we change
the id this id that side it can change
437.36 -> also that if we change it that side it could
not be changing also this side automatically
441.6 -> that's why i can see we put it on cascade
or delete so whenever we delete in there
446.88 -> in the parent table it's going
to disappear also from here
452.8 -> yeah guys that's the way we fix
this uh thanks for watching guys
457.2 -> uh see i hope i see you in the next video
please don't forget to subscribe don't forget to
463.36 -> to also give this uh uh send uh give this
to friends and share it today with them
470.32 -> post it on facebook on twitter and
everywhere make us popular guys
474.24 -> thanks for watching if we did help you on that
thanks for watching see you in the next video
Source: https://www.youtube.com/watch?v=edAfbueS77Q