Use index hint oracle
The Oracle INDEX hint instructs the optimizer to use an index scan for the specified table. Use the INDEX hint for function-based, domain, B-tree, bitmap, and bitmap join indexes. When working with tables containing ST_Geometry attributes and a st_spatial_index, specify the Oracle INDEX hint and the name of the st_spatial_index to instruct the optimizer to access the data by way of the index. Oracle provides the index hint, the and_equal hint, the index_asc hint, the index_combine hint, the index_desc hint, and the index_ffs hint to redirect the optimizer's use of indexes to access table rows. Let’s begin our discussion with the most common hint, the index hint. The Index Hint. This will tell oracle to use whatever indexes are available on table1 and table2 to generate the execution plan. SELECT /*+INDEX (table1 table1_index_name) INDEX (table2 table2_index_name)*/ FROM .. Remember though, that if you give the tables an alias, you have to use that in the hint rather than the actual table name There is an appropriate index on column_having_index, and its use actually increase performance, but Oracle didn't use it You should gather statistics on your table to let optimizer see that index access can help. Using direct hint is not a good practice. The easiest way to force index usage is with the index hint. When forcing an index, always use the table alias whenever you have a query that specifies an alias. For example, the following query will force the use of the dept_idx index because the emp table is aliased with "e": select /*+ index(e,dept_idx) */ * from emp e;
Use of the USE_NL and USE_MERGE hints is recommended with the ORDERED hint. Oracle uses these hints when the referenced table is forced to be the inner table of a join; the hints are ignored if the referenced table is the outer table.
The Oracle INDEX hint instructs the optimizer to use an index scan for the specified table. Use the INDEX hint for function-based, domain, B-tree, bitmap, and bitmap join indexes. When working with tables containing ST_Geometry attributes and a st_spatial_index, specify the Oracle INDEX hint and the name of the st_spatial_index to instruct the optimizer to access the data by way of the index. Oracle provides the index hint, the and_equal hint, the index_asc hint, the index_combine hint, the index_desc hint, and the index_ffs hint to redirect the optimizer's use of indexes to access table rows. Let’s begin our discussion with the most common hint, the index hint. The Index Hint. This will tell oracle to use whatever indexes are available on table1 and table2 to generate the execution plan. SELECT /*+INDEX (table1 table1_index_name) INDEX (table2 table2_index_name)*/ FROM .. Remember though, that if you give the tables an alias, you have to use that in the hint rather than the actual table name There is an appropriate index on column_having_index, and its use actually increase performance, but Oracle didn't use it You should gather statistics on your table to let optimizer see that index access can help. Using direct hint is not a good practice. The easiest way to force index usage is with the index hint. When forcing an index, always use the table alias whenever you have a query that specifies an alias. For example, the following query will force the use of the dept_idx index because the emp table is aliased with "e": select /*+ index(e,dept_idx) */ * from emp e;
2016年9月12日 Hint是Oracle資料庫中很有特色的一個功能，是很多DBA優化中經常採用的一個手段 。那為什麼Oracle 強制使用index skip scan的方式訪問索引。
28 Nov 2012 Hints are CBO directives. If Oracle can use the hint, it will only produce explain plans that contain the hint directive. This article examines index
For access path hints, Oracle ignores the hint if you specify the SAMPLE option the INDEX hint, the optimizer might not necessarily use that hint, because the
19 Jul 2010 Oracle still ignored the hint to use the IND_T15_C3 index, and selected to use the IND_T15_C1_C2 index instead (again). Oh, Oracle does not The only way of guaranteeing the use of indexes in these situations is to use an INDEX hint. EXISTS vs. IN. The EXISTS function searches for the presence of a If more than one index is provided, the indexes are separated by at least one space; the INDEX_COMBINE hint is recommended for this use case though.
The Oracle INDEX hint instructs the optimizer to use an index scan for the specified table. Use the INDEX hint for function-based, domain, B-tree, bitmap, and bitmap join indexes. When working with tables containing ST_Geometry attributes and a st_spatial_index, specify the Oracle INDEX hint and the name of the st_spatial_index to instruct the optimizer to access the data by way of the index.
If you force the use of the index with an hint, Oracle will do a full index scan. It will not be interesting for you.If your query has a sense, maybe your data model is not appropriate. Maybe a good way is to split you column nr_certificate in two columns. If it's possible, it will be easy to you after to have the good and quick query. What is the trick in Oracle force index? Answer: Given accurate CBO statistics, the Oracle optimizer will also choose the "best" index, and it's not always a good idea to force a specific index unless you are sure that the index will always be the fastest path to your rows. The easiest way to force index usage is with the index hint. You can prevent the use of an index on a column without hints by applying a function to it. You'll want to use a "no-op" function so the column values aren't changed. For numbers this could be adding zero, for strings appending the empty string: select * from t1,t2 where t1.id || '' =t2.id; The USE_NL hint causes Oracle to join each specified table to another row source with a nested loops join using the specified table as the inner table. The syntax of the USE_NL hint is USE_NL(table table) where table is the name or alias of a table to be used as the inner table of a nested loops join.
select /*+ index(customer cust_primary_key_idx) */ * from customer; Also note that of you alias the table, you must use the alias in the index hint: select /*+ 2011年9月6日 在SQL語句優化過程中，我們經常會用到hint,現總結一下在SQL優化過程中常見 Oracle hint的用法： 如果是要指定使用某個Index,則利用規則。 1. You can use the INDEX hint for domain, B-tree, bitmap, and bitmap join indexes. However, Oracle recommends using INDEX_COMBINE rather than INDEX for the The index hint is the key here, but the more up to date way of specifying it is with the column naming method rather than the index naming method