Search index for UTF8

Question

How i can organize search index for the varchar2 field in the table, when the coding page of the database is UTF8 ?

Answer 1

There are 2 ways to build linguistic indexes for data in multiple languages.
1. Build a linguistic index for each language which the application needs to support. This approach offers simplicity but requires more disk space. For each index, the rows in the language other than the one on which the index is built are collated together at the end of the sequence. The following example builds linguistic indexes for French and German.
CREATE INDEX french_index ON emp (NLSSORT(emp_name, 'NLS_SORT=FRENCH'));
CREATE INDEX german_index ON emp (NLSSORT(emp_name, 'NLS_SORT=GERMAN'));
Which index to use is based on the NLS_SORT session parameters or the arguments of the NLSSORT function you specified in the ORDER BY clause. For example, if the session variable NLS_SORT is set to FRENCH, you can use french_index and when it is set to GERMAN, you can use german_index.
2. Build a single linguistic index for all languages. This can be accomplished by
including a language column (LANG_COL in the example below) that contains NLS_LANGUAGE values for the corresponding column on which the index is built as a parameter to the NLSSORT function. The following example builds a single linguistic index for multiple languages. With this index, the rows with
the same values for NLS_LANGUAGE are collated together.
CREATE INDEX i ON t (NLSSORT(col, 'NLS_SORT=' | | LANG_COL));
Which index to use is based on the argument of the NLSSORT function you specified in the ORDER BY clause.