The PROCEDURE clause of SELECT passes the whole result set
to a Procedure which will process it. These Procedures are
not Stored Procedures, and can only be written in the C
language, so it is necessary to recompile the server.
 
Currently, the only available procedure is ANALYSE, which
examines the resultset and suggests the optimal datatypes
for each column. It is defined in the sql/sql_analyse.cc
file, and can be used as an example to create more
Procedures.
 
This clause cannot be used in a view's definition.
 


URL: https://mariadb.com/kb/en/procedure/