Mysql for cainiao: adding, modifying, and deleting Columns

Mysql for cainiao: adding, modifying, and deleting Columns

Test data:
 
 
 
I. Column addition:
1. alter table name column Declaration
The added columns are at the end of the table by default.
 
 
 
2. You can use "after" to specify which columns are behind the new columns.
 
 
 
3. If the new column is to be placed at the beginning of the table, use first
 
 
 
Ii. Column Modification

Alter table name change column name declaration to be modified

As shown in the table, the varchar length of name is 10, and now it is changed to 20.

 
 
 
 
 
Iii. Column deletion:

Alter table name: name of the column to be deleted

In this example, the height column is deleted as follows: