gistfile1.txt

# 結果取得を呼ばなければ単なるQueryオブジェクト
query = Entry.query.filter(Entry.id == 1) # => <class 'sqlalchemy.orm.query.Query'>

# クエリの付け加えもできる
if hoge == True:
    query = query.filter(Entry.text == "entry")

# hoge = True : SELECT * FROM entries WHERE entries.id = %s AND entries.text = %s
# hoge = False : SELECT * FROM entries WHERE entries.id = %s

# サブクエリ
sub_query = Entry.query.filter_by(text="entry").subquery()
db_session.query(sub_query).filter_by(id=1).all()

# SELECT *
# FROM (
#    SELECT * FROM entries
#       WHERE entries.text = "entry"
#    ) AS anon_1
# WHERE anon_1.id = 1

# Union
q1 = Entry.query.filter_by(id=1)
q2 = Entry.query.filter_by(id=2)
q1.union(q2).all()