In Oracle Database 12c, the operations related to dropping columns from a table include several behaviors, each specified clearly in Oracle documentation and best practices:
B. A column drop is implicitly committed: Dropping a column in Oracle using the ALTER TABLE ... DROP COLUMN command is a DDL (Data Definition Language) operation, which means it cannot be rolled back. DDL commands in Oracle are automatically and implicitly committed, meaning that once a column is dropped, the action is finalized immediately.
C. A column that is referenced by another column in any other table cannot be dropped: In Oracle, if a column is being referenced by a foreign key constraint or any dependency from another table, you cannot directly drop it until those references are removed or disabled. This ensures data integrity across related tables.
E. A primary key column cannot be dropped: The primary key constraint is critical for identifying unique rows within a table. Oracle does not allow the dropping of columns that are part of a primary key without first dropping the constraint or modifying it to exclude the column you intend to drop.
References:
Oracle Database SQL Language Reference 12c, specifically sections discussing DDL operations and constraints.
In Oracle Database 12c, the operations related to dropping columns from a table include several behaviors, each specified clearly in Oracle documentation and best practices:
B. A column drop is implicitly committed: Dropping a column in Oracle using the ALTER TABLE ... DROP COLUMN command is a DDL (Data Definition Language) operation, which means it cannot be rolled back. DDL commands in Oracle are automatically and implicitly committed, meaning that once a column is dropped, the action is finalized immediately.
C. A column that is referenced by another column in any other table cannot be dropped: In Oracle, if a column is being referenced by a foreign key constraint or any dependency from another table, you cannot directly drop it until those references are removed or disabled. This ensures data integrity across related tables.
E. A primary key column cannot be dropped: The primary key constraint is critical for identifying unique rows within a table. Oracle does not allow the dropping of columns that are part of a primary key without first dropping the constraint or modifying it to exclude the column you intend to drop.
References:
Oracle Database SQL Language Reference 12c, specifically sections discussing DDL operations and constraints.
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