大数据就业实战培训 Oracle就业实战培训
Oracle OCP 19c 认证1Z0-082考试题库(第16题)-CUUG内部学员版082题库解析
16.Which three statements are true about dropping and unused columns in an Oracle database?(Choose three.)
A. A primary key column referenced by another column as a foreign key can be dropped if using the CASCADE option.
B. An UNUSED column’s space is reclaimed automatically when the block containing that column is next queried.
C. An UNUSED column’s space is reclaimed automatically when the row containing that column is next queried.
D. Partition key columns cannot be dropped.
E. A DROP COLUMN command can be rolled back
F. A column that is set to UNUSED still counts towards the limit of 1000 columns per table
