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【青鸟飞扬教育】MySQL 是如何利用索引的
Sou Hu Cai Jing· 2025-06-15 23:11
Group 1 - The article discusses the confusion surrounding MySQL's ability to utilize indexes during SQL optimization, particularly in cases of range queries and LIKE operations [1] - It aims to clarify the conditions under which MySQL can effectively use indexes for sorting and filtering data [1] Group 2 - The key_len column in the EXPLAIN execution plan indicates the length of the selected index in bytes, which helps determine how many columns of a composite index are being utilized [2] - The calculation of key_len varies based on the data type, with specific byte lengths assigned to different types such as int (4 bytes) and bigint (8 bytes), and additional considerations for string types and NULL allowances [2] Group 3 - The article presents a model divided into three parts: Index Key, Index Filter, and Table Filter, which illustrate how MySQL determines the data range and filtering capabilities using indexes [4] - Index Key is used to establish the scanning range for MySQL, defined by upper and lower boundaries based on the conditions specified in the WHERE clause [5]