By Diana Lorentz
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It doesn't matter what DBMS you're using—Oracle, DB2, SQL Server, MySQL, PostgreSQL—misunderstandings can continually come up over the ideal meanings of phrases, misunderstandings which can have a significant influence at the good fortune of your database initiatives. for instance, listed below are a few universal database phrases: characteristic, BCNF, consistency, denormalization, predicate, repeating staff, subscribe to dependency.
Additional info for Oracle8i. SQL Reference. Release 8.1.5
The data object number is an identification number assigned to every database segment. You can retrieve the data object number from data dictionary views USER_OBJECTS, DBA_OBJECTS, and ALL_OBJECTS. Objects that share the same segment (clustered tables in the same cluster, for example) have the same object number. Extended rowids are not available directly. You can use a supplied package, DBMS_ ROWID, to interpret extended rowid contents. The package functions extract and provide information that would be available directly from a restricted rowid, as well as information specific to extended rowids.
When you create a table with an NVARCHAR2 column, you supply the maximum number of characters or bytes it can hold. Oracle subsequently stores each value in the column exactly as you specify it, provided the value does not exceed the column’s maximum length. The column’s maximum length is determined by the national character set definition. Width specifications of character datatype NVARCHAR2 refer to the number of characters if the national character set is fixed width and refer to the number of bytes if the national character set is variable width.
For more information about LOBs, see Oracle8i Application Developer’s Guide - Large Objects (LOBs) and Oracle Call Interface Programmer’s Guide. BLOB Datatype The BLOB datatype stores unstructured binary large objects. BLOBs can be thought of as bitstreams with no character set semantics. BLOBs can store up to 4 gigabytes of binary data. BLOBs have full transactional support. Changes made through SQL, the DBMS_ LOB package, or the OCI participate fully in the transaction. BLOB value manipulations can be committed and rolled back.