Oracle Database Tips by Donald Burleson

Table Alteration

Face it, no one designs perfect applications. This means we sometimes have to change things. For tables, this means adding, changing, or dropping columns; adding constraints; or even deleting all of the rows from the table. Let's look at how to accomplish these table changes using the functions of the Oracle8 ALTER TABLE command, which are to:

• Add a column.

• Add an integrity constraint.

• Add integrity constraints to object-type columns.

• Add or modify index-only table characteristics.

• Add or modify LOB columns.

• Add or modify object type, nested table type, or varray type column for a table.

• Add, modify, split, move, drop, or truncate table partitions.

• Add, modify, split, move, drop, or truncate table subpartitions.

• Allow or disallow writes to a table.

• Change the rows per block of storage for a table.

• Drop a column.

• Enable, disable, or drop an integrity constraint or trigger.

• Explicitly allocate an extent.

• Explicitly deallocate the unused space of a table.

• Modification of the degree of parallelism for a table

• Modify the LOGGING/NOLOGGING attributes.

• Modify the real storage attributes of a nonpartitioned table or the default attributes of a partitioned table.

• Modify the storage characteristics or other parameters.

• Physically move a table.

• Redefine a column (datatype, size, default value).

• Rename a table or a table partition.       

• In order to use the ALTER TABLE command in Oracle, the following must be true:

• The table must be in your own schema, you must have ALTER privilege on the table, or you must have ALTER ANY TABLE system privilege.

• To use an object type in a column definition when modifying a table, either that object must belong to the same schema as the table being altered or you must have either the EXECUTE ANY TYPE system or the EXECUTE schema object privilege for the object type.

• If you are using Trusted Oracle in DBMS MAC mode, your DBMS label must match the table's creation label or you must satisfy one of the following criteria:

a. If the table's creation label is higher than your DBMS label, you must have READUP and WRITEUP system privileges.

b. If the table's creation label is lower than your DBMS label, you must have the WRITEDOWN system privilege.

c. If the table's creation label and your DBMS label are not comparable, you must have READUP, WRITEUP, and WRITEDOWN system privileges.   

See Code Depot    

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