mysql show global variables字符超1024会被截断

show variables 会存在数据被截断的问题：

select 全局变量没有问题

官网解释：https://dev.mysql.com/doc/refman/5.6/en/variables-table.html

The VARIABLE_VALUE column for each of these tables is defined as VARCHAR(1024). For variables with very long values that are not completely displayed, use select as a workaround.

所以如果要写一些检测脚本，尽量用select 变量来查询，避免发生误判。