You are getting this constraint check because Ordre table does not have reference OrdreID provided in insert command. To insert value in Ordrelinje, you first have to enter value in Ordre table and use same OrdreID in Orderlinje table. Or you can remove not null constraint and insert a NULL value in it. Hope it helps!!
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.
If you are getting error Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails while using php artisan migrate command after creating a migration file. You can set foreign id column value as nullable with null on delete on delete parent table record.
MySQL error 1452 - Cannot add or update a child row: a foreign key constraint fails? This error comes whenever we add a foreign key constraint between tables and insert records into the child table.
Taken from Using FOREIGN KEY Constraints
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.
It will reject any INSERT or UPDATE operation that attempts to create a foreign key value in a child table if there is no a matching candidate key value in the parent table.
So your error Error Code: 1452. Cannot add or update a child row: a foreign key constraint fails
essentially means that, you are trying to add a row to your Ordrelinje
table for which no matching row (OrderID) is present in Ordre
table.
You must first insert the row to your Ordre
table.
The Problem is with FOREIGN KEY Constraint. By Default (SET FOREIGN_KEY_CHECKS = 1). FOREIGN_KEY_CHECKS option specifies whether or not to check foreign key constraints for InnoDB tables. MySQL - SET FOREIGN_KEY_CHECKS
We can set foreign key check as disable before running Query. Disable Foreign key.
Execute one of these lines before running your query, then you can run your query successfully. :)
1) For Session (recommended)
SET FOREIGN_KEY_CHECKS=0;
2) Globally
SET GLOBAL FOREIGN_KEY_CHECKS=0;
You are getting this constraint check because Ordre
table does not have reference OrdreID
provided in insert command.
To insert value in Ordrelinje
, you first have to enter value in Ordre
table and use same OrdreID
in Orderlinje
table.
Or you can remove not null constraint and insert a NULL value in it.
This error generally occurs because we have some values in the referencing field of the child table, which do not exist in the referenced/candidate field of the parent table.
Sometimes, we may get this error when we are applying Foreign Key constraints to existing table(s), having data in them already. Some of the other answers are suggesting to delete the data completely from child table, and then apply the constraint. However, this is not an option when we already have working/production data in the child table. In most scenarios, we will need to update the data in the child table (instead of deleting them).
Now, we can utilize Left Join
to find all those rows in the child table, which does not have matching values in the parent table. Following query would be helpful to fetch those non-matching rows:
SELECT child_table.*
FROM child_table
LEFT JOIN parent_table
ON parent_table.referenced_column = child_table.referencing_column
WHERE parent_table.referenced_column IS NULL
Now, you can generally do one (or more) of the following steps to fix the data.
null
as well.Once the data is fixed, we can apply the Foreign key constraint using ALTER TABLE
syntax.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With