MySQL adds a field deletion field, modifies the field name, and modifies the field type.

The simple Syntax of MySQL is commonly used, but it is not easy to remember. Of course, these SQL syntaxes are basically common in various databases. Listed below:

1. Add a field

Alter table user add column new1 varchar (20) default null; // Add a field, empty by default
Alter table user add column new2 varchar (20) not null; // Add a field, which cannot be blank by default.

2. delete a field
Alter table user drop column new2; // delete a field

3. modify a field
Alter table user modify new1 varchar (10); // modify the type of a field
Alter table user change new1 new4 int; // modify the name of a field. You must specify the field type again.

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