mysql 为某一数据库下所有表中添加相同字段

BEGIN
  DECLARE s_tablename VARCHAR(100);
 
 /*显示表的数据库中的所有表
 SELECT table_name FROM information_schema.tables WHERE table_schema='databasename' Order by table_name ;
 */

#显示所有
 DECLARE cur_table_structure CURSOR
 FOR
 SELECT table_name
 FROM INFORMATION_SCHEMA.TABLES
 WHERE table_schema = 'preschool'
 ORDER BY table_name;

DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET s_tablename = NULL;

OPEN cur_table_structure;

FETCH cur_table_structure INTO s_tablename;
 WHILE ( s_tablename IS NOT NULL) DO
  SET @MyQuery=CONCAT("alter table `",s_tablename,"` add column sharding_name VARCHAR(30)");
  PREPARE msql FROM @MyQuery;
 
  EXECUTE msql ;#USING @c;
   
  FETCH cur_table_structure INTO s_tablename;
  END WHILE;
 CLOSE cur_table_structure;

END