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Errors

Error 1452​

This error occurs when we try to add or update a row in a child table, but the referenced parent row does not exist.

Example: we have a table users and a table meals.

  • The users table has a column id (Primary Key).
  • The meals table has a column user_id (Foreign Key) that references users.id.

In relational databases, foreign keys define a parent-child relationship between two tables.

  • Parent table: The table that owns the primary key (e.g., users)
  • Child table: The table that contains a foreign key pointing to the parent (e.g., meals)

This error will occur if you try to insert a row into meals with a user_id that does not exist in the users table.

INSERT INTO meals (user_id) VALUES (1);

will only work if in the table users we have a row which contains id = 1.