插入数据
<?php # 创建连接 $conn = mysqli_connect("localhost", "root", "admin", "study"); # 查看是否连接成功 if ($conn) { echo "服务器连接成功!"; } else { echo mysqli_connect_error(); } # SQL语句, 向主表添加数据 $SQL1 = "INSERT INTO student (student_id, student_name) VALUES(1, '我是小白呀'), (2, '我是大白呀')"; # 执行SQL语句 $result = mysqli_query($conn, $SQL1); # SQL语句, 向从表添加数据 $SQL2 = "INSERT INTO grade (student_id, course, grade) VALUES(1, '语文', 59), (2, '语文', 99)"; # 执行SQL语句 $result = mysqli_query($conn, $SQL2); # 查看是否执行成功 if ($result) { echo "SQL语句执行成功!"; } else { echo mysqli_error($conn); } # 关闭连接 mysqli_close($conn); ?>
错误展示
<?php # 创建连接 $conn = mysqli_connect("localhost", "root", "admin", "study"); # 查看是否连接成功 if ($conn) { echo "服务器连接成功!"; } else { echo mysqli_connect_error(); } # SQL语句, 错误展示 (主表没有student_id=3) $SQL = "INSERT INTO grade (student_id, course, grade) VALUES(3, '语文', 88)"; # 执行SQL语句 $result = mysqli_query($conn, $SQL); # 查看是否执行成功 if ($result) { echo "SQL语句执行成功!"; } else { echo mysqli_error($conn); } # 关闭连接 mysqli_close($conn); ?>
报错:
服务器连接成功!
Fatal error: Uncaught mysqli_sql_exception: Cannot add or update a child row: a foreign key constraint fails (`study`.`grade`, CONSTRAINT `grade_ibfk_1` FOREIGN KEY (`student_id`) REFERENCES `student` (`student_id`)) in C:\Users\Windows\Desktop\数据库\外键错误.php:19
Stack trace:
#0 C:\Users\Windows\Desktop\数据库\外键错误.php(19): mysqli_query(Object(mysqli), 'INSERT INTO gra...')
#1 {main}
thrown in C:\Users\Windows\Desktop\数据库\外键错误.php on line 19
PHP Fatal error: Uncaught mysqli_sql_exception: Cannot add or update a child row: a foreign key constraint fails (`study`.`grade`, CONSTRAINT `grade_ibfk_1` FOREIGN KEY (`student_id`) REFERENCES `student` (`student_id`)) in C:\Users\Windows\Desktop\数据库\外键错误.php:19
Stack trace:
#0 C:\Users\Windows\Desktop\数据库\外键错误.php(19): mysqli_query(Object(mysqli), 'INSERT INTO gra...')
#1 {main}
thrown in C:\Users\Windows\Desktop\数据库\外键错误.php on line 19
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