Merge 3ca9990 into f9960d4

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "python.pythonPath": "/home/cpinamtz/.virtualenvs/pypika-fork/bin/python"
+}

pypika/terms.py

@@ -804,6 +804,23 @@ def negate(self) -> "ContainsCriterion":
         self._is_negated = True
 
 
+class ExistsCriterion(Criterion):
+    def __init__(self, container, alias=None):
+        super(ExistsCriterion, self).__init__(alias)
+        self.container = container
+        self._is_negated = False
+
+    def get_sql(self, **kwargs):
+        # FIXME escape
+        return "{not_}EXISTS {container}".format(
+            container=self.container.get_sql(**kwargs),
+            not_='NOT ' if self._is_negated else ''
+        )
+
+    def negate(self):
+        self._is_negated = True
+        return self
+
 class RangeCriterion(Criterion):
     def __init__(self, term: Term, start: Any, end: Any, alias: Optional[str] = None) -> str:
         super().__init__(alias)

pypika/tests/test_criterions.py

@@ -12,7 +12,7 @@
     functions as fn,
 )
 from pypika.queries import QueryBuilder
-from pypika.terms import Mod
+from pypika.terms import ExistsCriterion, Mod
 
 __author__ = "Timothy Heys"
 __email__ = "theys@kayak.com"
@@ -590,6 +590,27 @@ def test_glob_single_chars_and_various_chars(self):
         self.assertEqual('"like"."foo" GLOB \'a_b*\'', str(c2))
 
 
+class ExistsCriterionTests(unittest.TestCase):
+    t2 = Table("abc", alias="t2")
+    q2 = QueryBuilder().from_(t2).select(t2.field2)
+
+    def test_exists(self):
+        t1 = Table("def", alias="t1")
+        q1 = QueryBuilder().from_(t1).where(ExistsCriterion(self.q2)).select(t1.field1)
+
+        self.assertEqual(
+            'SELECT "t1"."field1" FROM "def" "t1" WHERE EXISTS (SELECT "t2"."field2" FROM "abc" "t2")', str(q1)
+        )
+
+    def test_not_exists(self):
+        t1 = Table("def", alias="t1")
+        q1 = QueryBuilder().from_(t1).where(ExistsCriterion(self.q2).negate()).select(t1.field1)
+
+        self.assertEqual(
+            'SELECT "t1"."field1" FROM "def" "t1" WHERE NOT EXISTS (SELECT "t2"."field2" FROM "abc" "t2")', str(q1)
+        )
+
+
 class ComplexCriterionTests(unittest.TestCase):
     table_abc, table_efg = Table("abc", alias="cx0"), Table("efg", alias="cx1")