Most Popular Indexes

All About the Basics of Indexes in Oracle 12c

An index is a simple concept. It is typically a listing of keywords accompanied by the location of information on a subject. To find information on indexes, for instance, you look up the word “indexes” in the index at the back of this book. It will give the number of the page you are reading […]

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How to Create a Bitmap Index in Oracle 12c

To help tune queries that use non-selective columns in their limiting conditions, you can use bitmap indexes. Bitmap indexes should only be used if the data is infrequently updated because they add to the cost of all data-manipulation transactions against the tables they index. NOTE Bitmap indexes should not be used for tables involved in […]

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Tips on Indexed Columns in Oracle 12c

Traditional (B*-tree) indexes are most useful on columns with a significant amount of variety in their data. For instance, a column that indicates whether a company is a current client with a Y or N value would be a poor choice for a traditional index and could actually slow down a query; a bitmap index […]

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How to Rebuild an Index in Oracle 12c

Oracle provides a fast index rebuild capability that allows you to re-create an index without having to drop the existing index. The currently available index is used as the data source for the index, instead of the table’s being used as the data source. During the index rebuild, you can change its STORAGE parameters and […]

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How to Use SQL Server Missing Indexes

SQL Server provides an approach that can help you find useful indexes for your existing queries. This option, called the Missing Indexes feature, does not require the database administrator to decide when tuning is needed, to explicitly identify what workload represents the load to tune, or to run any tool. This lightweight feature — introduced […]

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Use a SQL Server Clustered Index or a Heap?

One of the main decisions you have to make while creating a table is whether to use a clustered index or a heap. This is sometimes a topic for debate in the SQL Server community, and there is no right or wrong answer. Although the best solution may depend on your table definition and workload, […]

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How to Identify and Remove Unused SQL Server Indexes

Here we’ll introduce the functionality of the sys.dm_db_index_usage_stats DMV, which you can use to learn about the operations performed by your indexes. It is especially helpful in discovering indexes that are not used by any query, or are only minimally used. Indexes that are not being used will provide no benefit to your databases, but […]

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Improving Performance with MySQL Index Columns

In addition to creating new indexes to improve performance, you can improve database performance with additional schema optimizations. These optimizations include using specific data types and/or column types. The benefit is a smaller disk footprint producing less disk I/O and results in more index data being packed in available system memory. Data Types Several data […]

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Optimizing MySQL Indexes

The management of indexes—how they are created and maintained—can impact the performance of SQL statements. Combining Your DDL An important management requirement when adding indexes to MySQL is the blocking nature of a DDL statement. Historically, the impact of an ALTER statement required that a new copy of the table be created. This could be […]

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Performance Tuning for MySQL with Indexes

A surprising number of people in online forums request information about slow queries without having tried to add an index to a frequently accessed field. As you know from Chapter 3, tables with fields that are accessed frequently can be ordered by creating an index. An index points to the place on a database where […]

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Using MySQL Indexes

To speed up searches and reduce query execution time, MySQL lets you index particular fields of a table. The term “index” here means much the same as in the real world. Similar in concept to the index you find at the end of a book, an index is a list of sorted field values used […]

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What You Should Know About Limitations in MySQL Indexes

There are several limitations to how indexes are used and managed in MySQL in comparison to other RDBMS products. Cost Based Optimizer MySQL uses a cost based optimizer to prune the possible query tree to create the most optimal SQL execution path. MySQL has limited capabilities for using generated statistics to aid the optimizer as […]

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