SET statement in stored programs is an
extended version of the general
statement (see Section 12.4.4, “
SET Syntax”). Each
var_name may refer to a local
variable declared inside a stored program, a system variable, or
a user-defined variable.
SET statement in stored programs is
implemented as part of the pre-existing
syntax. This allows an extended syntax of
SET a=x, b=y,
... where different variable types (locally declared
variables, global and session system variables, user-defined
variables) can be mixed. This also allows combinations of local
variables and some options that make sense only for system
variables; in that case, the options are recognized but ignored.