在Oracle中,索引有包括很多类型。不同类型的索引适应不同的系统环境和访问场景。其中,唯一性索引UniqueIndex是我们经常使用到的一种。 唯一性索引unique index和一般索引normal index最大的差异就是在索引列上增加了一层唯一约束。添加唯一性索引的数据列可以为空,但是只要存在数据值,就必须是唯一的。 那么,在使用唯一...
当约束列上没有索引时,在创建unique constraint 时,oracle 会自动创建unique index,并且该索引不能删除,当删除unique constraint 时,unique index 会自动删除。 2.2 测试unique constraint 和non-unique index --现在字段phone上创建B-Tree索引 SYS@anqing2(rac2)> create indexidx_ut_phone on ut(phone); Index ...
In this tutorial, you will learn how to use Oracle unique index to prevent duplicate values in the indexed column or columns of a table.
Oracle Cloud Infrastructure - Database Service - Version N/A and laterOracle Database Backup Service - Version N/A and laterInformation in this document applies to any platform. Symptoms While rebuilding the index which is primary key of the table, we got following error: Cause Sign In To ...
--Oracle 自动创建了索引并关联到约束, 索引名和约束名是相同的。 --验证下索引 SYS@anqing2(rac2)> selectindex_name,index_type,uniqueness,generated from user_indexes wheretable_name='UT'; INDEX_NAME INDEX_TYPE UNIQUENES GENERATED --- --- --- UC_PHONE NORMAL UNIQUE N --我们并没有创建索引,...
唯一性索引（UniqueIndex）与普通索引（NormalIndex）差异（上） 个人分类：oracle工作机制 索引是我们经常使用的一种数据库搜索优化手段。适当的业务操作场景使用适当的索引方案可以显著的提升系统整体性能和用户体验。在Oracle中，索引有包括很多类型。不同类型的索引适应不同的系统环境和访问场景。其中，唯一性索引Uniqu...
CREATEUNIQUEINDEXindex_nameONtable_name(column_name); 3.Defining Foreign Key Constraints: ALTERTABLEchild_table ADDCONSTRAINTconstraint_nameFOREIGNKEY(column_name) REFERENCESparent_table(parent_column_name); Conclusion Oracle Unique offers a range of capabilities to enforce uniqueness and maintain data integ...
This place needs to pay attention to it, take a segment partition in the data dictionary, Oracle is assigned to the space, does not mean that all use. May two index structure difference is very small, but the extra allocation of a extent. Index of leaf structure, check the contents of ...
(normal index)差异(上)(唯一性索引 (single index 与普通索引 (standard index) 差异 (上)) Unique index (Unique Index) and common index (Normal Index) difference (on) The classification of individuals: the working mechanism of Oracle The index is a database search optimization method we often ...
Oracle implicitly creates a unique index on the corresponding attribute to support this constraint. However, this index can be problematic in a data warehouse for three reasons: The unique index can be very large, because the table can easily have millions or even billions of rows. ...