Drop Columns

Use alter table to drop a column from an existing table.

You can drop any number of columns using a single alter table statement. However, you cannot drop the last remaining column from a table (for example, if you drop four columns from a five-column table, you cannot then drop the remaining column).

alter table titles
drop advance, contract

alter table rebuilds all indexes on the table when it drops a column.

• Drop Columns Renumbers the Column ID
  alter table renumbers column IDs when you drop a column from a table. Columns with IDs higher than the number of the dropped column move down one column ID to fill the gap that the dropped column leaves behind.
• Drop Columns Without Performing a Data Copy
  The no datacopy parameter to the alter table drop column allows you to drop columns from a table without performing a data copy, and reduces the amount of time required for alter table drop column to run.
• Drop Constraints
  Use alter table to drop a constraint.