多选题Which statements are correct regarding indexes？ （）AWhen a table is dropped， the corresponding indexes are automatically dropped.BFor each DML operation performed， the corresponding indexes are automatically updated.CIndexes should be created on columns
题目
多选题
Which statements are correct regarding indexes？ （）
A
When a table is dropped， the corresponding indexes are automatically dropped.
B
For each DML operation performed， the corresponding indexes are automatically updated.
C
Indexes should be created on columns that are frequently referenced as part of an expression.
D
A non-deferrable PRIMARY KEY or UNIQUE KEY constraint in a table automatically creates a uniqueindex.