Previously, program options could be specified in full or as any unambiguous prefix. For example, the --compress option could be given to mysqldump as --compr, but not as --comp because the latter is ambiguous. Option prefixes now are deprecated. They can cause problems when new options are implemented for programs. A prefix that is currently unambiguous might become ambiguous in the future. If an unambiguous prefix is given, a warning now occurs to provide feedback. For example:
Warning: Using unique option prefix compr instead of compress is deprecated and will be removed in a future release. Please use the full name instead.
Option prefixes are no longer supported in MySQL 5.7; only full options are accepted. (Bug #16996656)
Mysql：Changes in MySQL 5.6.13 (2013-07-31, General Availability)：不再支持可能引起混乱的【选项缩略】写法！
原文：https://www.cnblogs.com/jinzhenshui/p/12591055.html