Uses of Function-Based Indexes (200)

Function-based indexes provide an efficient mechanism for evaluating statements that
contain functions in their WHERE clauses. The value of the expression is computed and
stored in the index. When it processes INSERT and UPDATE statements, however,
Oracle must still evaluate the function to process the statement.

Function-based indexes defined on UPPER(column_name) or LOWER(column_name) can facilitate
case-insensitive searches.

A function-based index can also be used for a globalization support sort index that
provides efficient linguistic collation in SQL statements.

使用函式索引
1. 如果一個 SQL 語句的 WHERE 子句中使用了函式，那麼建立相應的函式索引是提高資料訪問效能
2. 使用 UPPER(column_name) 或 LOWER(column_name) 函式建立函式索引需要注意大小敏感性

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