mysql 批量修改列的长度

-- mysql 批量修改列的长度
select
  concat(
    'alter table ',
    TABLE_SCHEMA,
    '.',
    TABLE_NAME,
    ' modify column ',
    COLUMN_NAME,
    ' varchar(64) ',
    ' not null  default \'\' ',
    ' comment \'',
    COLUMN_COMMENT,
    '\';'
  )
from
  information_schema.COLUMNS
where
  DATA_TYPE = 'varchar'
  and CHARACTER_MAXIMUM_LENGTH = 32
  and TABLE_SCHEMA = 'test';
  
  
-- 查询某个列长的设置为 
select concat('update ',TABLE_SCHEMA,'.',TABLE_NAME,' set ',COLUMN_NAME,' = ''''', ' where ' ,COLUMN_NAME, ' is null;')
 from information_schema.COLUMNS where DATA_TYPE='varchar' and CHARACTER_MAXIMUM_LENGTH=32 and TABLE_SCHEMA='test';