Mysql adds a column, deletes a column, modifies a column name, and mysql columns at a certain position in the table.

Mysql adds a column, deletes a column, modifies a column name, and mysql columns at a certain position in the table.

To add a column to a created table, run the following code: alter table name add column name varchar (20) not null; this statement adds a column to an existing table. This column is located in the last column of the table. If you want to add a column in the specified column, you can use: alter table name add column name varchar (20) not null after user1. Note, the preceding command adds the addr column to the end of the user1 column. If you want to add a column to the first column, you can use: alter table name add column name varchar (20) not null first; In the yusheng table, change the column name def to unitalter table yusheng change def unit char; Delete the column name def in the yusheng table alter table yusheng drop column def;