mysql - 获取数据库的最后更新返回 null (mysql)

Question

我需要获取数据库上次更改(更新、修改等)的时间我执行以下查询，但它为所有表返回 null。有什么问题吗？

SELECT 
    update_time 
FROM 
    information_schema.tables 
WHERE 
    table_schema = 'myschema' 

Answer 1

作为 information_schema.tables 上的 MySQL 文档说(强调):

Beginning with MySQL 5.7.2, UPDATE_TIME displays a timestamp value for the last UPDATE, INSERT, or DELETE performed on InnoDB tables that are not partitioned. Previously, UPDATE_TIME displayed a NULL value for InnoDB tables. For MVCC, the timestamp value reflects the COMMIT time, which is considered the last update time. Timestamps are not persisted when the server is restarted or when the table is evicted from the InnoDB data dictionary cache.

The UPDATE_TIME column also shows this information for partitioned InnoDB tables in MySQL 5.7.8 and later. Previously this column was always NULL for such tables. (Bug #17299181, Bug #69990)

可能您正在使用 innodb 表并且您的 MySQL 版本早于文档中描述的版本。