Oracle drop column purge

Notice that the PURGE clause does not allow you to roll back or recover the table that you dropped. Therefore, it is useful if you don’t want the sensitive data to appear in the recycle bin. If you drop a composite-partitioned table, then all the partitions and subpartitions are also dropped.

When you drop a partitioned table with the PURGE keyword , the statement executes as a series of subtransactions, each of which drops a subset of partitions or subpartitions and their metadata. To physically drop a column you can use one of the following syntaxes, depending on whether you wish to drop a single or multiple columns. The process of dropping a column from a big table can be time and resource consuming. ALTER TABLE table_name.

So it’s better to mark column as unused and can be deleted after some time. The PURGE option will purge the table and its dependent objects so that they do not appear in the recycle bin. The risk of specifying the PURGE option is that you will not be able to recover the table.

But still occupied the memory in database so to release the the memory for another object we can use the the Purge clause. To drop a column from a table you can use one of these syntax examples, depending on whether you wish to drop a single column (with drop column ) or multiple columns. Use the PURGE statement to remove a table or index from your recycle bin and release all of the space associated with the object, or to remove the entire recycle bin, or to remove part of all of a dropped tablespace from the recycle bin.

Remember, when you drop a table column the column space remains used inside the data blocks and you may want to reorganize the table (using the dbms_redefinition package) to reclaim the free spaced from the dropped table column. Oracle alter table drop column. How to drop a table in SQL?

How do I create a table in SQL? What is Cascade constraint? Use the DROP TABLE statement to move a table or object table to the recycle bin or to remove the table and all its data from the database entirely. Caution: Unless you specify the PURGE clause, the DROP TABLE statement does not result in space being released back to the tablespace for use by other objects, and the space continues to count. In huge tables the process of dropping columns from table is really very time consuming.

Once you mark the column as unused you can longer see that column in oracle table. It also consumes lot of resources and slows down the performance. The above syntax is supported by MySQL and PostgreSQL. That is, if a column has ever had a default value assigned to it, then the DATA_DEFAULT column of the USER_TAB_COLUMNS data dictionary view will always display either a default value or NULL. By default, when you drop a table, it is placed in your recycle bin.

That allows you to undrop the table if you discover that you dropped a table inadvertently. You can prevent a table from going to the recycle bin by using the PURGE clause, i. When you drop a global partitioned index, a range-partitioned index, or a hash-partitioned index, all the index partitions are also dropped. The storage is still being used of course and you still need to purge to free it, it just looks a bit more consistent in the data dictionary. So this looks like a (very minor) bug, maybe, at most. However, the benefit of using PURGE is that you can ensure.

It is not possible to drop the unused column when using table compression and. Primary Key, indee this is not dropped neither once that the alter. After you have moved all partitions with nocompress option, you can drop column (s) issuing: alter table tdrop column colstatement, or. Every now and then you may want to remove a column from a table. Dropping unused columns: Make colunused.

Maybe the business has realised each toy has many colours. Thus you want remove this column. This is an expensive. If you use the user-defined name of the table, and there are multiple tables with the same name, then the purge command will purge the objects with that name.

Once a foreign key has been create you may find that you wish to drop the foreign key from the table.