Which of the following statements about indexes is TRUE?
Answer:
a. Columns with low cardinality are handled well by B-tree indexes.
b. Columns with low cardinality are handled poorly by Bitmap indexes.
c. Columns with high cardinality are handled poorly by Bitmap indexes.
d. Columns with high cardinality are handled well by B-tree indexes.
???
Answer:
a. Columns with low cardinality are handled well by B-tree indexes.
b. Columns with low cardinality are handled poorly by Bitmap indexes.
c. Columns with high cardinality are handled poorly by Bitmap indexes.
d. Columns with high cardinality are handled well by B-tree indexes.
???
我只知道如果一个列重复值特别多,比如:性别 用bitmap
如果,重复的非常少,用b-tree