SQL Error wp_commentmeta – incorrect table definition

I am not sure where you got that export code but I don’t see the PRIMARY KEY defined as it should be. Take a look at the code from Core that creates the table:

87  CREATE TABLE $wpdb->commentmeta (
88    meta_id bigint(20) unsigned NOT NULL auto_increment,
89    comment_id bigint(20) unsigned NOT NULL default '0',
90    meta_key varchar(255) default NULL,
91    meta_value longtext,
92    PRIMARY KEY  (meta_id),
93    KEY comment_id (comment_id),
94    KEY meta_key (meta_key($max_index_length))
95  ) $charset_collate;

Take a look at line 92. That is missing from your “create” statement.