常用sql

1. insert.. select
   eg. insert into tb1 select * from tb2 ;

2. create … like
   eg. create tb1 like tb2;

3. 查看所有库中包含指定字段的所有表

   select * from information_schema where column_name='xxx';
   
   -- 指定db
   select * from information_schema where column_name='xxx' and table_schema='xxdb';

4. 批量修改表字段类型

   select CONCAT('alter table  ',TABLE_SCHEMA,'.',TABLE_NAME,'  
   modify `', COLUMN_NAME, '` bigint(20) ',  
   ' default ', COLUMN_DEFAULT, ' COMMENT  '' , COLUMN_COMMENT, '';') 
   from information_schema.COLUMNS 
   where  COLUMN_NAME = 'first_order_id';