2023年12月8日发(作者：)

Unknownsystemvariablequery_cache_size错误原因以及解决办法

Error querying database. Cause: GetJdbcConnectionException: Could not get JDBC Connection; nested exception is tedException: Cannot create PoolableConnectionFactory

### The error may exist in file [/Volumes/mac/Eclipse Project/Tomcat_version/apache-tomcat-9.0.21/webapps/chuan_zang_help/WEB-INF/classes/cn/ydyfc/chuan_zang_help/mapper/]

### The error may involve _zang_AllAdmins

### The error occurred while executing a query

### Cause: GetJdbcConnectionException: Could not get JDBC Connection; nested exception is tedException: Cannot create PoolableConnectionFactory (Unknown system var

eption: Unknown system variable 'query_cache_size'

at SQLException(:964)

at rrorPacket(:3973)

at rrorPacket(:3909)

at mmand(:2527)

错误提示：Cannot create PoolableConnectionFactory (Unknown system variable 'query_cache_size')

原因：由于mysql驱动包的版本过低导致这个问题的发生意思是query cache在MySQL5.7.20就已经过时了，而在MySQL8.0之后就已经被移除了。

我改成8以上才可以了。