How to Define an Auto Increment Primary Key in Oracle
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The index used to enforce a primary key DOES NOT HAVE TO BE unique. A PK will not.
In case you want to discuss it more, please send me the type of objects getting invalidated and the oracle version. It is entirely possible with later releases of Oracle to use a non-unique index to enforce a primary key constraint. If you want the table to be implemented as an IOT index organized table it will be physically ordered by the primary key. Followup July 23, 2004 - 8:19 am UTC give me a for exmaple.
How to Define an Auto Increment Primary Key in Oracle - Yes, there would be no problem, if all PKs where created during table creation, i. And actually thanks to that the DELETE TRANDATA is now possible and works.
You tend to use the primary key as the most natural unique identifier for a row such as social security number, employee ID and so forth, although there is a school of thought that you should always use an artificial surrogate key for this. Indexes, on the other hand, can be used for fast retrieval based on other columns. For example, an employee database may have your employee number as the primary key but it may also have an index on your last name or your department. Both of these indexes last name and department would disallow NULLs probably and allow duplicates almost certainly , and they would be useful to speed up queries looking for anyone with for example the last name 'Corleone' or working in the 'HitMan' department. Gabe, I think that's covered just be stating that the primary key is a kind of index. Stating that an index is indexed seems a little superfluous to me, but if you can come up with a workable change I couldn't but that may just be a limitation of mine , I'll welcome the input. An index is a performance optimisation feature that enables data to be accessed faster. Keys are frequently good candidates for indexing and some DBMSs automatically create indexes for keys, but that doesn't have to be so. However the set of attributes in question are not necessarily a key because they may not be unique. Oracle Database enforces a UNIQUE key or PRIMARY KEY integrity constraint on a table by creating a unique index on the unique key or primary key. This index is automatically created by the database when the constraint is enabled. You can create indexes explicitly outside of integrity constraints using the SQL statement CREATE INDEX. Indexes can be unique or non-unique. Unique indexes guarantee that no two rows of a table have duplicate values in the key column or columns. Non-unique indexes do not impose this restriction on the column values. Use the CREATE UNIQUE INDEX statement to create a unique index. Specifying the Index Associated with a Constraint If you require more explicit control over the indexes associated with UNIQUE and PRIMARY KEY constraints, the database lets you: 1. Specify an existing index that the database is to use to enforce the constraint 2. Specify a CREATE INDEX statement that the database is to use to create the index and enforce the constraint These options are specified using the USING INDEX clause. Example: CREATE TABLE a a1 INT PRIMARY KEY USING INDEX create index ai on a a1 ;.
Now only I came to know that, Foreign key can be created for table with unique constraint. By all means -- if something is a primary key CALL IT THAT. The developer who made the patch is celebrating his victory. The index used to enforce a primary key DOES NOT HAVE TO BE unique. It seems that messing with PRIMARY KEY and UNIQUE INDEX causes GoldenGate to do strange things with transactions. The unique index will be the best but a non-unique index will also be a better option as compared to a full table scan. But the constraint name would still be there. In my experience with new tables, or tables without indexes, a primary key constraint always creates an index with the same name. Most people get these wrong.
