OUT parameters in PREPARE

Current — 10.1.1 — implementation of OUT parameters in PREPARE is as follows:

PREPARE .... "SELECT ... INTO ?, ?, ...";

EXECUTE .... USING @var1, @var2, ...

It is non-standard. And it's not strictly necessary, as there are easy workarounds.

Standard syntax is

PREPARE .... "SELECT ... ";

EXECUTE ... INTO @var1, @var2, ...

The workaround is:

PREPARE .... "SELECT ... INTO @var1, @var2, ...";

EXECUTE ....

We should consider changing the syntax to be standard or removing this feature completely.