英文原文

those are not columns you can modify, they are metadata propertes of each user column the database needs to work, your columns you can modify are Fname, Lname, age and phone.

The console output confusingly calls them Fields but they are your user columns for that table you have called mytable. What you are seeing and thinking are columns are metadata properties of the fields. Each field has a type, is nullable, is a key, has an optional default value, and some extra data. These are things the database needs to operate.

From the MySQL Reference Manual

If you want to find out about the structure of a table, the DESCRIBE

statement is useful; it displays information about each of a table's

columns:

mysql> DESCRIBE pet;

+---------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+---------+-------------+------+-----+---------+-------+

| name | varchar(20) | YES | | NULL | |

| owner | varchar(20) | YES | | NULL | |

| species | varchar(20) | YES | | NULL | |

| sex | char(1) | YES | | NULL | |

| birth | date | YES | | NULL | |

| death | date | YES | | NULL | |

+---------+-------------+------+-----+---------+-------+

Field indicates the column name, Type is the data type for the column,

NULL indicates whether the column can contain NULL values, Key

indicates whether the column is indexed, and Default specifies the

column's default value. Extra displays special information about

columns: If a column was created with the AUTO_INCREMENT option, the

value will be auto_increment rather than empty.

If you want to see the DATA in your table then use Select instead of Describe; see the above explanation of what Describe actually does.

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