我有 x 行计数，但所有索引基数都比 x 大得多，这怎么可能？如果我理解正确，索引基数是该索引的唯一行数。
最佳答案
来自 SHOW INDEX :
Cardinality
An estimate of the number of unique values in the index. This is updated by running ANALYZE TABLE or myisamchk -a. Cardinality is counted based on statistics stored as integers, so the value is not necessarily exact even for small tables.
关于mysql索引基数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/3337625/