Indexes can greatly improve the performance of searches on the indexed column(s). However, indexes take up space within the database and slow down insert, update, and delete operations. This section helps you determine when you should create an index and how to achieve maximum performance from your index.

There are many situations in which creating an index improves the performance of a database. An index provides an ordering of a table's rows based on the values in some or all of the columns. An index allows SQL Anywhere to find rows quickly. It permits greater concurrency by limiting the number of database pages accessed. An index also affords SQL Anywhere a convenient means of enforcing a uniqueness constraint on the rows in a table.

When creating indexes, the order in which you specify the columns becomes the order in which the columns appear in the index. Duplicate references to column names in the index definition is not allowed.

The Index Consultant is a tool that assists you in the selection of an appropriate set of indexes for your database. See Index Consultant.