Kolom MySQL yang didefinisikan dengan NOT NULL memungkinkan nulls

Saya telah membuat tabel beberapa waktu lalu dan mulai menambahkan data ke dalamnya. Baru-baru ini saya menambahkan kolom baru ( address) ke dalamnya dengan NOT NULLsebagai bagian dari kolom baru. Baris lama (pra-penambahan) masih nol, yang membuat peringatan sebagai bagian dari definisi. Namun, baris baru dengan kolom baru masih diizinkan untuk memasukkan nol.

Apakah pra-penambahan kolom baru nulls sumbernya diizinkan? Jika demikian, apakah ada cara untuk memberi tahu MySQL untuk tidak mengizinkannya meskipun sebelumnya?

mysql> show create table my_table\G
*************************** 1. row ***************************
       Table: my_table
Create Table: CREATE TABLE `my_table` (
  `entry_id` int(11) NOT NULL auto_increment,
  `address` varchar(512) NOT NULL,
  `follow_up_to` int(11) default NULL,
  PRIMARY KEY  (`entry_id`),
  KEY `follow_up_to` (`follow_up_to`),
  CONSTRAINT `my_table_ibfk_1` 
     FOREIGN KEY (`follow_up_to`) 
     REFERENCES `my_table` (`entry_id`) ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=535 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql>

Versi mysql apa ini?

Mode apa yang Anda jalankan?

SELECT @@GLOBAL.SQL_MODE, @@SESSION.SQL_MODE;

(Ini harus dijalankan dalam konteks aplikasi Anda, kalau-kalau itu mengubahnya).

MySQL didokumentasikan sebagai berikut: http://dev.mysql.com/doc/refman/5.0/id/data-type-defaults.html

As of MySQL 5.0.2, if a column definition includes no explicit DEFAULT value, MySQL determines the default value as follows:

If the column can take NULL as a value, the column is defined with an explicit DEFAULT NULL clause. This is the same as before 5.0.2.

If the column cannot take NULL as the value, MySQL defines the column with no explicit DEFAULT clause. For data entry, if an INSERT or REPLACE statement includes no value for
the column, MySQL handles the column according to the SQL mode in effect at the time:

If strict SQL mode is not enabled, MySQL sets the column to the implicit default value for the column data type. 

Pengujian saya sendiri gagal menduplikasi masalah Anda

mysql> CREATE TABLE `my_table` (
    ->   `entry_id` int(11) NOT NULL AUTO_INCREMENT,
    ->   `address` varchar(512) NOT NULL,
    ->   `follow_up_to` int(11) DEFAULT NULL,
    ->   PRIMARY KEY (`entry_id`),
    ->   KEY `follow_up_to` (`follow_up_to`)
    -> ) ENGINE=InnoDB AUTO_INCREMENT=536 DEFAULT CHARSET=latin1;
Query OK, 0 rows affected, 2 warnings (0.16 sec)

mysql> INSERT INTO my_table VALUES (NULL, NULL, NULL);
ERROR 1048 (23000): Column 'address' cannot be null
mysql> INSERT INTO my_table (follow_up_to) VALUES (NULL);
Query OK, 1 row affected, 1 warning (0.10 sec)

mysql> SHOW WARNINGS;
+---------+------+----------------------------------------------+
| Level   | Code | Message                                      |
+---------+------+----------------------------------------------+
| Warning | 1364 | Field 'address' doesn't have a default value |
+---------+------+----------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT * FROM my_table;
+----------+---------+--------------+
| entry_id | address | follow_up_to |
+----------+---------+--------------+
|      537 |         |         NULL |
+----------+---------+--------------+
1 row in set (0.00 sec)

Fakta bahwa data lama memiliki null seharusnya tidak menjadi masalah. Tabel Alter seharusnya 'memotong' nulls menjadi string kosong

mysql> SHOW CREATE TABLE my_table\G
*************************** 1. row ***************************
       Table: my_table
Create Table: CREATE TABLE `my_table` (
  `entry_id` int(11) NOT NULL AUTO_INCREMENT,
  `address` varchar(512) NOT NULL,
  `follow_up_to` int(11) DEFAULT NULL,
  PRIMARY KEY (`entry_id`),
  KEY `follow_up_to` (`follow_up_to`)
) ENGINE=InnoDB AUTO_INCREMENT=536 DEFAULT CHARSET=latin1
1 row in set (0.04 sec)

mysql> ALTER TABLE my_table MODIFY address VARCHAR(512) NULL DEFAULT NULL;
Query OK, 1 row affected (0.76 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> INSERT INTO my_table VALUES (NULL, NULL, NULL), (NULL, NULL, NULL);
Query OK, 2 rows affected (0.05 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM my_table;
+----------+---------+--------------+
| entry_id | address | follow_up_to |
+----------+---------+--------------+
|      535 |         |         NULL |
|      536 | NULL    |         NULL |
|      537 | NULL    |         NULL |
+----------+---------+--------------+
3 rows in set (0.04 sec)

mysql> ALTER TABLE my_table MODIFY address VARCHAR(512) NOT NULL;
Query OK, 3 rows affected, 2 warnings (0.83 sec)
Records: 3  Duplicates: 0  Warnings: 2

mysql> SHOW WARNINGS;
+---------+------+----------------------------------------------+
| Level   | Code | Message                                      |
+---------+------+----------------------------------------------+
| Warning | 1265 | Data truncated for column 'address' at row 2 |
| Warning | 1265 | Data truncated for column 'address' at row 3 |
+---------+------+----------------------------------------------+
2 rows in set (0.04 sec)

mysql> SELECT * FROM my_table;
+----------+---------+--------------+
| entry_id | address | follow_up_to |
+----------+---------+--------------+
|      535 |         |         NULL |
|      536 |         |         NULL |
|      537 |         |         NULL |
+----------+---------+--------------+
3 rows in set (0.04 sec)

mysql> INSERT INTO my_table VALUES (NULL, NULL, NULL), (NULL, NULL, NULL);
Query OK, 2 rows affected, 2 warnings (0.08 sec)
Records: 2  Duplicates: 0  Warnings: 2

mysql> SELECT * FROM my_table;
+----------+---------+--------------+
| entry_id | address | follow_up_to |
+----------+---------+--------------+
|      535 |         |         NULL |
|      536 |         |         NULL |
|      537 |         |         NULL |
|      538 |         |         NULL |
|      539 |         |         NULL |
+----------+---------+--------------+
5 rows in set (0.05 sec)