Oracle

INDEXES

Figo Kim 2006. 11. 26. 11:51
336x280(권장), 300x250(권장), 250x250, 200x200 크기의 광고 코드만 넣을 수 있습니다.

An Index:

  • Is a schema object
  • Can be used by the Oracle server to speed up the retrieval of rows by using a pointer.
  • Can reduce disk I/O by using a rapid path access method to locate data quickly
  • Is independent of the table that it indexed
  • Is used and maintained automatically by the Oracle server
  1. Unique Index : Primary Key or Unique : automatically create an index
  2. NOnunique Index : User created index. ex) FOREIGN KEY

- If there is no INDEX, then a full table scan occurs.
- If you drop a table, corresponding indexes are also dropped.

Types of Indexes
  1. Unique Index : The Oracle server automatically creates this index when you define a column in a table to have a PRIMARY KEY or UNIQUE key constraint.
  2. Nonunique Index : This is an index that a user create.

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