set @v1a="Hello";
set @v2a="World";
set @v3a=65;
set @v4a=NULL;
select @v1a, @v2a, @v3a, @v4a, @v_unknown;
@v1a @v2a @v3a @v4a @v_unknown
Hello World 65 NULL NULL
select VARIABLE_NAME, VARIABLE_VALUE
from performance_schema.user_variables_by_thread
inner join performance_schema.threads
on user_variables_by_thread.thread_id=threads.thread_id
where threads.processlist_id=connection_id()
order by VARIABLE_NAME;
VARIABLE_NAME VARIABLE_VALUE
v1a Hello
v2a World
v3a 65
v4a NULL
connect con1, localhost, root,,;
set @v1b="Salut";
set @v2b="La compagnie";
set @v3b=12;
set @v4b=NULL;
select @v1b, @v2b, @v3b, @v4b, @v_unknown;
@v1b @v2b @v3b @v4b @v_unknown
Salut La compagnie 12 NULL NULL
select VARIABLE_NAME, VARIABLE_VALUE
from performance_schema.user_variables_by_thread
inner join performance_schema.threads
on user_variables_by_thread.thread_id=threads.thread_id
where threads.processlist_id in ($default_id, connection_id())
order by VARIABLE_NAME;
VARIABLE_NAME VARIABLE_VALUE
v1a Hello
v1b Salut
v2a World
v2b La compagnie
v3a 65
v3b 12
v4a NULL
v4b NULL
connection default;
disconnect con1;
select VARIABLE_NAME, VARIABLE_VALUE
from performance_schema.user_variables_by_thread
order by VARIABLE_NAME;
VARIABLE_NAME VARIABLE_VALUE
v1a Hello
v2a World
v3a 65
v4a NULL
set @blob_under_16_bits=repeat("a", 65000);
set @blob_under_24_bits=repeat("a", 1000000);
select length(@blob_under_16_bits);
length(@blob_under_16_bits)
65000
select length(@blob_under_24_bits);
length(@blob_under_24_bits)
1000000
select variable_name, length(variable_value)
from performance_schema.user_variables_by_thread
where VARIABLE_NAME like "blob%"
  order by VARIABLE_NAME;
variable_name length(variable_value)
blob_under_16_bits 65000
blob_under_24_bits 1000000
set @a=10;
CREATE procedure test_user_val
(IN input INT,OUT output INT)
BEGIN
SELECT input + input
INTO output;
END|
CALL test_user_val(@a , @total);
select VARIABLE_NAME,VARIABLE_VALUE from performance_schema.user_variables_by_thread 
where variable_name in ('a','total') order by VARIABLE_NAME;
VARIABLE_NAME VARIABLE_VALUE
a 10
total 20
create table t1 (c1 int);
CREATE TRIGGER test_uvar_trigger
AFTER INSERT ON t1
FOR EACH ROW BEGIN
set @a=@a+@a;
END|
insert into t1 values(1);
select VARIABLE_NAME,VARIABLE_VALUE from performance_schema.user_variables_by_thread 
where variable_name ='a' order by VARIABLE_NAME;
VARIABLE_NAME VARIABLE_VALUE
a 20
insert into t1 values(1);
select VARIABLE_NAME,VARIABLE_VALUE from performance_schema.user_variables_by_thread 
where variable_name ='a' order by VARIABLE_NAME;
VARIABLE_NAME VARIABLE_VALUE
a 40
drop table t1;
drop procedure test_user_val;