MySQL命令显示所有可供查询的分类

mysql> ? contents;You asked for help about help category: "Contents"For more information, type 'help ', where  is one of the followingcategories:   Account Management   Administration   Compound Statements   Data Definition   Data Manipulation   Data Types   Functions   Functions and Modifiers for Use with GROUP BY   Geographic Features   Help metadata   Language Structure   Plugins   Procedures   Storage Engines   Table Maintenance   Transactions   User-Defined Functions   Utilitymysql>