record counting

[dotJoon]

myTable1

(id)
 1
 2
 3
 4
 5

myTable1

(in) (out)

 2    1
 3    1
 4    1
 5    2

I have myTables like the above.

When a variables is 1, the query below produces the result below.

code

SELECT id
FROM myTable1 mm 
WHERE mm.id<>1
AND mm.id IN (SELECT myTable2.in FROM myTable2 WHERE myTable2.out=1)

result

2
3
4

I like to know the number of the result above in SQL.
The trial code1 below seems not to work.

trial code1
SELECT count(*) as count
FROM myTable1 mm 
WHERE mm.id<>1
AND mm.id IN (SELECT myTable2.in FROM myTable2 WHERE myTable2.out=1)

target result

3

If I should use GROUP BY for getting COUNT, how can I use GROUP BY in this case?


The trial code2 and the trial code3 below are all failed.

trial code2
SELECT count(*) as count
FROM myTable1 mm 
WHERE mm.id<>1
AND mm.id IN (SELECT myTable2.in FROM myTable2 WHERE myTable2.out=1)
GROUP BY myTable2.out

trial code3
SELECT count(*) as count
FROM myTable1 mm 
WHERE mm.id<>1
AND mm.id IN (SELECT myTable2.in FROM myTable2 WHERE myTable2.out=1)
GROUP BY myTable2.in

[guido2004]

The trial code1 below seems not to work.

Care to explain what 'seems not to work' mean? Do you get an error? Do you get a result different from 3? If so, what result do you get?