SELECT objart, COUNT(*) AS "Number of objects"
FROM "SchemaA".table_1
GROUP BY objart
UNION
SELECT objart, COUNT(*)
FROM "SchemaA".table_2
GROUP BY objart
UNION
SELECT objart, COUNT(*)
FROM "SchemaA".tanle_3
GROUP BY objart
UNION
SELECT objart, COUNT(*)
FROM "SchemaA".table_4
GROUP BY objart
UNION
SELECT objart, COUNT(*)
FROM "SchemaA".table_5
GROUP BY objart
ORDER BY objart;