DataBase 修改表字段名稱

Sql Server

sp_rename 'tableName.columnName','new_columnName','column';

alter table cost drop column file_dir;
alter table cost add file_dir nvarchar(500);
alter table tablename alter column columnname nvarchar(64);

mysql

alter table cost drop column file_dir;
alter table cost add file_dir nvarchar(500);
alter table cost change file_dir file_dir_new nvarchar(50);