A new field in the MYSQL table specifies the location. How to write SQL statement?

The SQL statement used to add fields to the data table is written as follows:

1, change table name. Add field type is not empty. Default value is 0.

2. Change the table staff? Supplement? Spbh varchar(20) NOT NULL The default value is 0.

3. Add spbh to the employee table? Type is varchar, size 20 is not empty, and the default value is 0.

Extended data:

Other commonly used sql statements:

1. Modify the properties of fields in the data table and add comments to them.

Statement format: comment the column? What are the library name, table name and field name? Entered comments'; ?

Example: I want to be in the ers_data library? Add comments to the document_type field of the test table. The sql statement is:

The annotation on columns _ data.test.document _ type is "file type";

2. Delete the fields in the data table.

Statement format: alter table? Table name? Drop (field);