無法添加或更新子項，外鍵錯誤

我對 MySQL 比較陌生。我試圖在關係數據庫中插入值。我知道我必須先插入父表，然後才能在子表中插入。假設我們有名為 STATE、COUNTRY 的表。

START TRANSACTION;
INSERT INTO country (countryName, nationality,countryPrefix)
SELECT * FROM (SELECT 'Togo' AS countryName, 'Togolese' AS nationality, '228' AS countryPrefix) AS tmp
WHERE NOT EXISTS (
   SELECT countryName FROM country WHERE countryName = 'Togo'
) LIMIT 1;
SELECT country.idcountry FROM country WHERE country.countryName = 'Togo';
INSERT INTO state (stateName, country_idcountry)
SELECT * FROM (SELECT 'Region Maritime' AS stateName, '12' AS country_idcountry) AS tmp
WHERE NOT EXISTS (
   SELECT stateName FROM state WHERE stateName = 'Region Maritime'
) LIMIT 1;
COMMIT;

下圖是我遇到的錯誤的螢幕截圖。

此消息來自您嘗試插入連接表中不存在的數據

在你的情況下

您嘗試將12插入為國家/地區表中不存在的 County_id_contry。

所以你必須先在你的國家表中插入 12，然後再添加到國家表中

引用自：https://dba.stackexchange.com/questions/265978