read_only 表示是否允许普通用户写入。如果为on，表示禁止普通用户写入。
super_read_only 表示是否禁止超级用户写入，包括普通用户，即针对所有用户。
默认关闭。
如果打开 super_read_only，则read_only会自动打开。
如果关闭 read_only，则 super_read_only 会自动关闭。
下面做下测试。
super_read_only = 0, read_only=0
查看当前值：
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 0 |
+-------------------+-------------+
1 row in set (0.01 sec)
设置super_read_only=1之后，查看read_only的变化。
>set global super_read_only=1;
Query OK, 0 rows affected (0.00 sec)
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 1 | 1 |
+-------------------+-------------+
1 row in set (0.01 sec)
read_only变为1。
超级用户设置为只读后，自然普通用户也会设置只读。
super_read_only=0, read_only=1
查看当前值：
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 1 |
+-------------------+-------------+
1 row in set (0.00 sec)
设置 super_read_only=1后, 查看read_only 变化。
>set global super_read_only=1;
Query OK, 0 rows affected (0.00 sec)
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 1 | 1 |
+-------------------+-------------+
1 row in set (0.00 sec)
read_only无变化。
super_read_only=1, read_only=0
不存在这种情况。
super_read_only=1, read_only=1
查看当前值：
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 1 | 1 |
+-------------------+-------------+
1 row in set (0.00 sec)
设置super_read_only = 0之后, 查看read_only变化。
>set global super_read_only=0;
Query OK, 0 rows affected (0.01 sec)
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 1 |
+-------------------+-------------+
1 row in set (0.00 sec)
super_read_only = 0, read_only=0
查看当前值：
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 0 |
+-------------------+-------------+
1 row in set (0.01 sec)
设置read_only=1之后，查看super_read_only 有无变化。
>set global read_only=1;
Query OK, 0 rows affected (0.00 sec)
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 1 |
+-------------------+-------------+
1 row in set (0.00 sec)
super_read_only = 1, read_only=0
不存在这种情况。
super_read_only = 0, read_only=1
查看当前值：
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 1 |
+-------------------+-------------+
1 row in set (0.00 sec)
设置 read_only=0后，查看super_read_only有无变化。
>set global read_only=0;
Query OK, 0 rows affected (0.00 sec)
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 0 |
+-------------------+-------------+
1 row in set (0.01 sec)
super_read_only变为 0。
普通用户关闭只读，超级用户的只读（也包括普通用户）也自然会关闭只读。
super_read_only = 1, read_only=1
查看当前值：
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 1 | 1 |
+-------------------+-------------+
1 row in set (0.01 sec)
设置read_only=0之后，查看 super_read_only的变化。
>set global read_only=0;
Query OK, 0 rows affected (0.00 sec)
>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
| 0 | 0 |
+-------------------+-------------+
1 row in set (0.01 sec)
super_read_only变为 0。
总结
关于 read_only 与 super_read_only之间的关系，实际上从其定义就可以明白。
基础很重要。