SQL additions, deletions and modifications

USE sqlxx
CREATE TABLE ygb(
        sid INT,
        sname VARCHAR(20),
        sgender VARCHAR(2),
        sbirthday DATE,
        semail VARCHAR( 10 ),
        sremark VARCHAR(50)
        )
 DESC ygb;
 SELECT * FROM ygb;
  /* Add age column */
 ALTER TABLE ygb ADD COLUMN sage INT;
 /* Change the attribute of the age column to int */
 ALTER TABLE ygb MODIFY COLUMN sage INT;
 /* Change the varchar of email to 50 */ 
 ALTER TABLE ygb MODIFY COLUMN semail VARCHAR( 50 );
  /* delete the remark column */
 ALTER TABLE ygb DROP COLUMN sremark;
 /* Change the name of name to username */ 
 ALTER TABLE ygb CHANGE COLUMN sname username VARCHAR( 20 )
  /* Add data to the column, in order */ 
 INSERT INTO ygb VALUES( 123,'Han Kai','male' ,'2018-05-01','[email protected]',27 )
 INSERT INTO ygb VALUES( 213,'Xiaohan','Male','2018-01-01','[email protected]',24 )
 INSERT INTO ygb VALUES( 312,'Xiao Zhang','Male','2018-03-17','[email protected]',25 )
  /* Delete the row with id 213 */ 
 DELETE FROM ygb WHERE sid =213 ;
 DELETE FROM ygb WHERE username ='Han Kai' ;
  /* Change the gender of the row whose id is 312 to female and the name to Zhang Le */ 
 UPDATE ygb SET sgender ='female',username='Zhang Le' WHERE sid=312 ;