Assignment order for SQL SERVER update

1) First variable and then field

SET NOCOUNT on;

DECLARE @i int, @j int
DECLARE @Table Table
(
Id1 INT,
Id2 INT
);

INSERT @Table (ID1, ID2)
SELECT 1, 10
UNION All
SELECT 2, 20
UNION All
SELECT 3, 30;

SELECT @i = 1, @j = 0
UPDATE @Table SET Id1 = @i, Id2 = Id1, @i = @i + 1
SELECT * from @Table

SELECT @i = 1, @j = 0
UPDATE @Table SET Id1 = @i, Id2 = @j, @j = @i + ten, @i = @i + 1
SELECT * from @Table

SET NOCOUNT off;
Results:
Id1 ID2
----------- -----------
2 1
3 2
4 3

Id1 ID2
----------- -----------
2 11
3 12
4 13

2 between variables, from left to right

SET NOCOUNT on;

DECLARE @i int, @j int
DECLARE @Table Table
(
Id1 INT,
Id2 INT
);

INSERT @Table (ID1, ID2)
SELECT 1, 10;

SELECT @i = 1, @j = 0
UPDATE @Table SET @j = @i, @i = @i + 1
PRINT ' @i = ' + cast (@i as VARCHAR) + ', @j = ' + cast (@j as VARCHAR)

SELECT @i = 1, @j = 0
UPDATE @Table SET @i = @i + 1, @j = @i
PRINT ' @i = ' + cast (@i as VARCHAR) + ', @j = ' + cast (@j as VARCHAR)

SELECT @i = 1, @j = 0
UPDATE @Table SET @i = @j + 1, @j = @i
PRINT ' @i = ' + cast (@i as VARCHAR) + ', @j = ' + cast (@j as VARCHAR)

SELECT @i = 1, @j = 0
UPDATE @Table SET @i = @j, @j = @i
PRINT ' @i = ' + cast (@i as VARCHAR) + ', @j = ' + cast (@j as VARCHAR)

SET NOCOUNT off;
Results:
@i = 2, @j = 1
@i = 2, @j = 2
@i = 1, @j = 1
@i = 0, @j = 0

3) Between fields, parallel execution

SET NOCOUNT on;

DECLARE @Table Table
(
ID1 int, Id2 int
);

INSERT @Table (ID1, ID2)
SELECT 1, 10
UNION All
SELECT 2, 20
UNION All
SELECT 3, 30;

UPDATE @Table SET Id1 = Id2, Id2 = Id1
SELECT * from @Table

SET NOCOUNT off;
Results:
Id1 ID2
----------- -----------
10 1
20 2
30 3