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As a result, queries take timesometimes an annoyingly long time.
Nevertheless, if you don't use indexes, in many cases you're just wasting your time trying to improve performance by other means.Figure 4.2 shows the same table, but with the addition of an index on the value.Now, instead of searching through the table row by row looking for items that match, we can use the index.Let's consider how an index works by beginning with a table that has no indexes.
An unindexed table is simply an unordered collection of rows.
These are abstract notions that make no reference to the underlying representation a database system uses to operate on the data in your tables.