Oracle 面试题与答案
相关差异对比
问题 26. What is an Integrity Constrains?
An integrity constraint is a declarative way to define a business rule for a column of a table.
问题 27. What is an Index?
An Index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.
问题 28. What is an Extent?
An Extent is a specific number of contiguous data blocks, obtained in a single allocation, and used to store a specific type of information.
问题 29. What is a View?
A view is a virtual table. Every view has a Query attached to it. (The Query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)
问题 30. What is Table?
A table is the basic unit of data storage in an ORACLE database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.
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