DB2 Constraint

informational constraint：不影响DML操作，又可以用于DB2优化,约束有用。

用法：普通constraint后添加 not enforced enable query optimization

例如：

create table employee

(empid integer not null,

name  varchar(25),

gender char(1) not null,

constraint gender_ok check (gender in('M','F')) not enforced enable query optimization)

 

关闭：alter table employee alter check gender_ok disable query optimization

 

类型：

1. Relational Index

2. Spatial Grid Index

3. Dynamic Bitmap Index

4. Block Base Index

5. Xml Index