1. Index not used on Tables in views coderanch.comSajee, I know that several DBMSs -- including Oracle and IBM DB2 (latest versions) -- contain "query optimizers". Depending on the way they are configured, they may rewrite the query you enter, in order to maximize its efficiency. Sometimes, it is more efficient for a query to do a "full table scan" than to use the index. Hence, it is quite ... |
2. Can you have 3 indexes in one table? coderanch.comYou can have more indexes than columns.. Oracle allows you to have multi column indexes (indeed, in some situations, they are preferred). So, you could have an index for each column, and indexes for combo's of columns. Whats the down side? More indexes means longer insert times, but frankly, this is far, far outweighted by the benefits. Keep in mind, that ... |
3. Creating an index for a table. coderanch.comI'm trying to create an index for a table. I'm trying to figure out the best way to do this. I came out with two options. Are they basically the same? Or is there something that I don't notice. 1.) ALTER IGNORE TABLE `MYTABLENAME` ADD UNIQUE INDEX `unique_key` (`COLUMN_A`, `COLUMN_B`, `COLUMN_C`, `COLUMN_D`, `COLUMN_E`);"); 2.) ALTER IGNORE TABLE `MYTABLENAME` ADD UNIQUE KEY ... |
5. where is the index table gone coderanch.comI'd read a primer on database indexes (ask Google). Some systems offer meta-data tables that contain information about the indexes, but aren't actually the index. For example, in some software creating an index would add a line to a table to show the existence of the index. But this is purely representational. |
6. creating a temporary index on a table through code coderanch.comGenerally, index creation/deletion is a DDL command and it should be possible to run such command from JDBC, yes. However, this really is not a good idea. Although the details may vary depending on the database, building an index is rather expensive operation. Certainly the whole of the table will have to be read and the index, which is a complicated ... |
7. Index tables java-forums.orgHello, I have a few questions regarding index tables with MSSQL Server Express 2008. I will be guessing a bit here... As far as I understand, index tables are automatically created for primary keys (maybe other keys, too?). You can, however, create your own index tables for columns that are often used for searching - such as unique columns - in ... |