What Causes 'Cannot add or update a child row: a foreign key constraint fails' Errors?

Database integrity constraint conflict: understanding the outer key error

outer key constraints to ensure data integrity through the relationship between the maintenance table. When trying to operate data that violates these constraints, a "complete constraint conflict" error occurs.

In this example, you encounter an error: "Can't add or update sub -line: outer key constraints fail". This shows that the value you try to insert into the Comments table violates the external key constraints.

outer keys in the database mode

Check your database mode, and you will notice that the Comments table has an outer key constraint on the external key Project_id column, which references the ID column in the Projects table. This means that each value of the Project_id column in the Comments table must exist in the ID column of the Projects table.

The conflict occurred in the query

The mysql statement you try to insert a line into the Comments table, and its Project_id is '50dc845a-83E4-4DB3-8705-5432ae7aaee3'. However, this value does not exist in the ID column of the Projects table. As a result, the external key constraints are violated. Solving the conflict

To solve this problem, you need to ensure that the Project_id value is valid and existing in the corresponding column of the Projects table. Verify whether this value exists in the Projects table, and correspondingly corrects the value of inserting the statement.

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