java.sql.SQLIntegrityConstraintViolationException:无法添加或更新子行:外键约束失败(library.book_loans、约束book_loans_ibfk_3外键(isbn)引用book (isbn))
book_loans \x{e76f} `loan_id` int(11) NOT NULL, `Card_ID` med
我试图在以下两个表之间创建一个外键:
id (PK,null,unique,AI)..。(没有约束的其他列)
id (pk,null,unique,AI)..。student (student_number) ON DELETE CASCADE ON UPDATE CASCADE;错误1452 (23000):无法添加或更新子行:外键约束失败
public static void createAI() AI a = new AI(10,10,15,15); AI b= new AI(100,100,15,15);这只显示b;但是这会打印出a。public static void createAI() AI a = new AI(10</em