create table t(
a int,
b int without system versioning
) with system versioning;
insert into t values(1, 2);
insert into t values(3, 4);
select * from t;
a	b
1	2
3	4
select a from t for system_time as of timestamp now(6);
a
1
3
select a, b, b+0 from t for system_time as of timestamp now(6);
a	b	b+0
1	NULL	NULL
3	NULL	NULL
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
Warning	4075	Attempt to read unversioned field `b` in historical query
select * from t for system_time as of timestamp now(6);
a	b
1	NULL
3	NULL
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select count(*) from t group by b query for system_time as of timestamp now(6);
count(*)
2
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select * from t for system_time as of timestamp now(6) order by b asc;
a	b
1	NULL
3	NULL
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select * from t for system_time as of timestamp now(6) order by b desc;
a	b
1	NULL
3	NULL
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select * from t group by a having a=2 query for system_time as of timestamp now(6);
a	b
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select * from t group by b having b=2 query for system_time as of timestamp now(6);
a	b
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select a from t where b=2 query for system_time as of timestamp now(6);
a
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select a from t where b=NULL query for system_time as of timestamp now(6);
a
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select count(*), b from t group by b having b=NULL query for system_time as of timestamp now(6);
count(*)	b
Warnings:
Warning	4075	Attempt to read unversioned field `b` in historical query
select a, b from t;
a	b
1	2
3	4
drop table t;