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本文详细介绍了MySQL如何利用索引来快速查找特定列值的行，包括B树和R树等不同类型的索引，以及在查询优化、JOIN操作、排序和分组等方面的应用。通过索引，MySQL能更有效地减少需要检查的行数，提高查询性能。
MySQL :: MySQL 5.7 Reference Manual :: 8.3.1 How MySQL Uses Indexes
8.3.1 How MySQL Uses Indexes
Indexes are used to find rows with specific column values quickly. Without an index, MySQL must begin with the first row and then read through the entire table to find the relevant rows. The larger the table, the more this costs. If the table has an index for the columns in question, MySQL can quickly determine the position to seek to in the middle of the data file without having to look at all the data. This is much faster than reading every row sequentially.
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