You explain:
I get result 1453 only when all items in column attributeY are empty for 1453.
But that's incorrect. Bold emphasis mine. The aggregate function count returns (per documentation):
number of input rows for which the value of expression is not null
The same is true for SQLite (per documentation):
The count(X) function returns a count of the number of times that X is
not NULL in a group.
You obviously have one or more rows with a non-null value in attributeY in your Postgres table - probably an empty string ''.
Test with:
SELECT *
FROM myschema.table
WHERE attributeX = 1453
AND attributeY IS NOT NULL;
Be sure to understand the difference between "empty" ('') and NULL:
Empty strings are character types (typically text, varchar or char) with 0 characters ('') - so basically "nothing", the equivalent of 0 for a numeric data type. NULL is possible for any data type and means "unknown". Some clients have a hard time making the difference clear in their display.
Alternative query
To find attributeX where all attributeY are either empty or NULL use this alternative query:
SELECT attributeX
FROM myschema.table
GROUP BY attributeX
HAVING NOT bool_or(attributeY <> '');
The expression attributeY <> '' is only true for non-null, non-empty attributeY. The aggregate function bool_or returns (per documentation):
true if at least one input value is true, otherwise false
Those are the results we exclude (NOT ...) and return the rest. Voilá.
There are many other (less elegant) ways to achieve the same. Like:
... HAVING count(CASE WHEN attributeY <> '' THEN 1 END) = 0;
... HAVING count(attributeY <> '' OR NULL) = 0;
... HAVING count(NULLIF(attributeY, '') = 0;
More:
The documentation page you linked to is for the current version (3.8.9) of SQLite.
You could dig up the old version of cli.html for 3.7.13, but at that time, .import was pretty much undocumented.
Best Answer
If your table can contain a lot of rows, you can win some time with