似一块扣肉的博客

项目中存在数据量较大的流水数据，对流水数据进行按日，7日，30日，本月，本年等维度进行统计时，存在sql慢的问题，针对这一问题，对这类sql进行时间维度的优化，加索引，优化时间查询语句例：查询今日内数据 （50万数据条测试）优化前select a.time from tablewhere to_days(a.time) >= to_days(now())优化前sql运行0.734秒通过explain进行查询rows有50万条索引优化给table表的time字段加上index索引

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:Communications link failurecom.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has

Error querying database. Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column 'ie_llyh.u.ChkPlanID'; this is incompatible with sql_mode=only_full