将数据添加到表时出现 MySQL 错误 1452

Question

I get the following error when trying to import data via MySQL Workbench:

Preparing...
Importing DataInputs.sql...
Finished executing script
ERROR 1452 (23000) at line 6: Cannot add or update a child row: a foreign key constraint fails (`nsldatabase`.`player`, CONSTRAINT `playsFor` FOREIGN KEY (`player_ID`) REFERENCES `team` (`team_ID`))
Operation failed with exitcode 1

I am creating the database via two different SQL scripts. One creates the tables, and another imports the data. I thought initially that some foreign key wasn't define properly, but it seems like they are all setup properly. Any help would be great. See both files below:

This is the NSLStructure.sql file:

DROP DATABASE IF EXISTS NSLdatabase;

CREATE SCHEMA IF NOT EXISTS NSLdatabase;
USE NSLdatabase;



CREATE TABLE player (
  player_ID int NOT NULL,
  player_Name text NOT NULL,
  player_Position text NOT NULL,
  player_Skills int NOT NULL,
  team_ID int NOT NULL,
  CONSTRAINT playerPK PRIMARY KEY (player_ID)
);

CREATE TABLE history (
  history_ID int NOT NULL,
  player_ID int NOT NULL,
  history_Desc text NOT NULL,
  history_sDate text NOT NULL,
  history_eDate text NOT NULL,
  CONSTRAINT recordPK PRIMARY KEY (history_ID, player_ID)
);

CREATE TABLE field (
  field_ID int NOT NULL,
  field_Name text NOT NULL,
  field_Location text NOT NULL,
  CONSTRAINT fieldPK PRIMARY KEY (field_ID)
);

CREATE TABLE team (
  team_ID int NOT NULL,
  team_Name text NOT NULL,
  team_City text NOT NULL,
  field_ID int NOT NULL,
  captain_ID int NOT NULL,
  team_coach text NOT NULL,
  CONSTRAINT teamPK PRIMARY KEY (team_ID)
);

CREATE TABLE matches (
  matches_ID int NOT NULL,
  matches_Date text NOT NULL,
  matches_Score text NOT NULL,
  matches_Winner text NOT NULL,
  field_ID int NOT NULL,
  teamHost_ID int NOT NULL,
  teamGuest_ID int NOT NULL,
  CONSTRAINT matchesPK PRIMARY KEY (matches_ID)
);

CREATE TABLE goal (
  goal_ID int NOT NULL,
  goal_Time int NOT NULL,
  matches_ID int NOT NULL,
  player_ID int NOT NULL,
  CONSTRAINT goalPK PRIMARY KEY (goal_ID, matches_ID, player_ID)
);

ALTER TABLE team
  ADD CONSTRAINT capitanRel FOREIGN KEY (captain_ID)
  REFERENCES player (player_ID);

ALTER TABLE team
  ADD CONSTRAINT playedOnField FOREIGN KEY (field_ID)
  REFERENCES field (field_ID);

ALTER TABLE player
  ADD CONSTRAINT playsFor FOREIGN KEY (player_ID)
  REFERENCES team (team_ID);

ALTER TABLE history
  ADD CONSTRAINT hasRel FOREIGN KEY (player_ID)
  REFERENCES player (player_ID);

ALTER TABLE goal
  ADD CONSTRAINT scoredBy FOREIGN KEY (player_ID)
  REFERENCES player (player_ID);

ALTER TABLE goal
  ADD CONSTRAINT scoredIn FOREIGN KEY (matches_ID)
  REFERENCES matches (matches_ID);

ALTER TABLE matches
  ADD CONSTRAINT playedOn FOREIGN KEY (field_ID)
  REFERENCES field (field_ID);

ALTER TABLE matches
  ADD CONSTRAINT playedHost FOREIGN KEY (teamHost_ID)
  REFERENCES team (team_ID);

ALTER TABLE matches
  ADD CONSTRAINT playedGuest FOREIGN KEY (teamGuest_ID)
  REFERENCES team (team_ID);

This is the DataInputs.sql file:

USE NSLdatabase;

INSERT INTO player
  VALUES
  (1, "Paxton Pomykal", "Midfielder", 7.5, 1);

INSERT INTO history
  VALUES
  (1, 3, "US 20 Squad", "11/27/2003", "12/19/2003");

INSERT INTO field
  VALUES
  (1, "Dicks Sporting Goods Park", "Commerce City, CO");

INSERT INTO team
  VALUES
  (2, "Colorado Rapids", "Denver, CO", 1, 3, "Robin Fraser");

INSERT INTO matches
  VALUES
  (1, "01/08/2019", "0-1", 2, 1, 1, 2);

INSERT INTO goal
  VALUES
  (1, 32, 1, 19);

Answer 1

You are not inserting the data in the correct sequence. Parent rows need to be created before children rows, so the foreign key constraints are not violated.

So, typically, you need to create rows in team rows before creating rows in player . There may be other dependencies that you need to look into, based on the same logic.

An alternative approach would be to add the foreign key constraints after the data is inserted. However, I would not necessarily recommend that: if your data has invalid relationships, you will not be able to create the foreign keys. It is safer to proceed the other way around, since offending rows are immediately signaled.