mysql statistics function and database information_schema/performance_schema

 

1. Deduplicate the number of rows in the statistics table:

select count(distinct col_name) from table_name;

2. Count the number of rows

select count(*) from table_name;

3. You can use the mysql database INFORMATION_SCHEMA to query various information about the database or data table

4. There is also a default database PERFORMANCE_SCHEMA, which is mainly used to collect database server performance parameters

 

The database INFORMATION_SCHEMA provides a way to access database metadata. Metadata is data about the data, such as database name or table name, column data type, or access rights, etc.

 

refer to:

1、https://blog.csdn.net/XavierDarkness/article/details/77196714