Mysql Index Establishment need to note the following details _mysql

1. The timing of indexing: If a field in a table appears in Select, Filter, and sort criteria, it is worthwhile to index the field.

2. For a vague query like '%xxx ', a normal index is not satisfied and needs to be set up for Full-text indexing.

3. For multiple conditions, such as: "... where a=xxx and b=yyy", "... where a=xxx order by B", "... where a=xxx GROUP by B". You need to use a composite index. However, a composite index can only be used in a SQL statement that satisfies the "leftmost prefix" condition. Combined indexes have some side effects, such as the size of the index may be larger than the data itself, because there are many combination entries for the combined index. So in practical applications, to be tailored, using slow query analysis tool analysis.

4. Open the index cache, find the index directly in memory, no more disk.

5. Indexing is a cost, and when the update, DELETE statements are executed, the index is updated, which consumes more time. You can use the Mysqlreport report to understand the percentages of the Select, Update, delete, INSERT, and replace statements.