创建唯一性约束，自动创建了和约束名一样的唯一性索引

创建check约束，不会产生索引

创建外键约束，不会产生索引

启用约束:
enable( validate) :启用约束,创建索引,对已有及新加入的数据执行约束.
enable novalidate :启用约束,创建索引,仅对新加入的数据强制执行约束,而不管表中的现有数据.
禁用约束:
disable( novalidate):关闭约束,删除索引,可以对约束列的数据进行修改等操作.
disable validate :关闭约束,删除索引,不能对表进行插入/更新/删除等操作.

enable\validate用到的地方
1、物化视图要实现查询重写时，则必须保证相关联表的主外键约束的状态为enable、validate
2、要实现星型转换时，必须保证fact表即主表字段的外键约束的状态为enable、validate

SQL> alter table SALES disable novalidate constraint SALES_CHANNEL_FK;
Table altered.

SQL> select constraint_name,constraint_type,status,validated from user_constraints where table_name='SALES' and constraint_type='R' and CONSTRAINT_NAME='SALES_CHANNEL_FK';
CONSTRAINT_NAME CONSTRAINT_TYPE STATUS VALIDATED
-------------------- -------------------- ---------- --------------------
SALES_CHANNEL_FK R DISABLED NOT VALIDATED

SQL> alter table SALES disable validate constraint SALES_CHANNEL_FK;
Table altered.

SQL> select constraint_name,constraint_type,status,validated from user_constraints where table_name='SALES' and constraint_type='R' and CONSTRAINT_NAME='SALES_CHANNEL_FK';
CONSTRAINT_NAME CONSTRAINT_TYPE STATUS VALIDATED
-------------------- -------------------- ---------- --------------------
SALES_CHANNEL_FK R DISABLED VALIDATED

SQL> alter table SALES enable novalidate constraint SALES_CHANNEL_FK;
Table altered.

SQL> select constraint_name,constraint_type,status,validated from user_constraints where table_name='SALES' and constraint_type='R' and CONSTRAINT_NAME='SALES_CHANNEL_FK';
CONSTRAINT_NAME CONSTRAINT_TYPE STATUS VALIDATED
-------------------- -------------------- ---------- --------------------
SALES_CHANNEL_FK R ENABLED NOT VALIDATED

SQL> alter table SALES enable validate constraint SALES_CHANNEL_FK;
Table altered.

SQL> select constraint_name,constraint_type,status,validated from user_constraints where table_name='SALES' and constraint_type='R' and CONSTRAINT_NAME='SALES_CHANNEL_FK';
CONSTRAINT_NAME CONSTRAINT_TYPE STATUS VALIDATED
-------------------- -------------------- ---------- --------------------
SALES_CHANNEL_FK R ENABLED VALIDATED

ITPub博客

约束会自动创建索引吗,约束的validate和able

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