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This article mainly shows you "mysql how to add fields", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "how to add fields in mysql" this article.

In mysql, the statement to add a field is "ALTER TABLE table name ADD new field name data type constraint", the ALTER command is used to modify the data table name or modify the data table field, and the field is added at the end of the data by default.

The operating environment of this tutorial: windows10 system, mysql8.0.22 version, Dell G3 computer.

A MySQL data table is made up of rows and columns. The "column" of the table is usually called a Field, and the "row" of a table is called a Record. As the business changes, you may need to add new fields to existing tables.

MySQL allows you to add fields at the beginning, middle, and end.

A complete field includes the field name, data type, and constraints. The syntax format of the MySQL add field is as follows:

ALTER TABLE ADD [constraint]

The syntax format is described as follows:

Is the name of the data table

The name of the field to be added

The data type that can store data for the field to be added

[constraints] are optional and are used to constrain added fields.

By default, this syntax format adds a new field at the end of the table (after the last column).

Note: in this section we only add new fields and do not pay attention to its constraints.

Example 1

Create a new student data table in the test database, and the SQL statement and run result are as follows:

Mysql > USE test;Database changedmysql > CREATE TABLE student (- > id INT (4),-> name VARCHAR (20),-> sex CHAR (1); Query OK, 0 rows affected (0.09 sec)

Use DESC to view the student table structure, the SQL statement and the run result are as follows:

Mysql > DESC student +-+ | Field | Type | Null | Key | Default | Extra | +-+- -+ | id | int (4) | YES | | NULL | name | varchar (20) | YES | | NULL | | sex | char (1) | YES | | NULL | | +-+-+ 3 rows in set (0.01sec)

Use the ALTER TABLE statement to add a field of type INT age,SQL statement and run the result as follows:

Mysql > ALTER TABLE student ADD age INT (4); Query OK, 0 rows affected (0.16 sec) Records: 0 Duplicates: 0 Warnings: 0

Use DESC to view the structure of the student table and verify that the age field is added successfully. The SQL statement and the run result are as follows:

Mysql > DESC student +-+ | Field | Type | Null | Key | Default | Extra | +-+- -+ | id | int (4) | YES | | NULL | | name | varchar (20) | YES | | NULL | | sex | char (1) | YES | | NULL | | age | int (4) | YES | | NULL | | +-- -+ 4 rows in set (0.00 sec)

As you can see from the running results, the age field has been added to the student table, and the field is in the last position of the table, and the field is added successfully.

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