|11.5.2.You can set parameters for a stored procedure|
[IN|OUT|INOUT] <name> <data type>
If you don't specify IN, OUT, or INOUT for the parameter, it will default to IN.
An IN parameter is passed into the stored procedure to use internally.
An OUT parameter is set within the procedure, but accessed by the caller.
An INOUT parameter is passed into the procedure for internal use, but is also available to the caller after the procedure has completed.
The name and data type of the parameter are used in the stored procedure for referencing and setting values going in and out of the procedure.
The data type can be any valid data type for MySQL.