secure_file_priv 是一个和安全相关的参数
初始时最好设为空
secure_file_priv=“”
详细说明：
This variable is used to limit the effect of data import and export operations, such as those performed by the LOAD DATA and SELECT … INTO OUTFILE statements and the LOAD_FILE() function.
一般情况下设置为某个目录，如果目录不存在，则mysql可能无法启动
如果设为空，则不限制文件的操作