set unused

Use the column set unused option tag no longer in use

Use drop unsused columns marked as unused discarded column

 

alter table tabName set unused column  colName;

或alter table tabName set unused (colName);

alter table tabName  drop unused columns;

 

Usage scenarios: 1 business is in use, use the statement to alter table tabName drop column colName; will lock table, the use of business impact, especially in particularly large table