From b436bdb594fad3134ce6eba2219809faf1472c6e Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Mon, 23 Mar 2020 13:31:06 -0700
Subject: [PATCH] Fixed bug with null columns, closes #95

---
 sqlite_utils/utils.py              | 11 ++++++++---
 tests/test_create.py               |  6 ++++++
 tests/test_suggest_column_types.py |  1 +
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/sqlite_utils/utils.py b/sqlite_utils/utils.py
index d086ddb..ecb3568 100644
--- a/sqlite_utils/utils.py
+++ b/sqlite_utils/utils.py
@@ -13,11 +13,16 @@ def suggest_column_types(records):
     all_column_types = {}
     for record in records:
         for key, value in record.items():
-            if value is not None:
-                all_column_types.setdefault(key, set()).add(type(value))
+            all_column_types.setdefault(key, set()).add(type(value))
     column_types = {}
+
     for key, types in all_column_types.items():
-        if len(types) == 1:
+        # Ignore null values if at least one other type present:
+        if len(types) > 1:
+            types.discard(None.__class__)
+        if {None.__class__} == types:
+            t = str
+        elif len(types) == 1:
             t = list(types)[0]
             # But if it's a subclass of list / tuple / dict, use str
             # instead as we will be storing it as JSON in the table
diff --git a/tests/test_create.py b/tests/test_create.py
index 92e0f8a..905f49d 100644
--- a/tests/test_create.py
+++ b/tests/test_create.py
@@ -813,3 +813,9 @@ def test_insert_all_empty_list(fresh_db):
     assert 1 == fresh_db["t"].count
     fresh_db["t"].insert_all([], replace=True)
     assert 1 == fresh_db["t"].count
+
+
+def test_create_with_a_null_column(fresh_db):
+    record = {"name": "Name", "description": None}
+    fresh_db["t"].insert(record)
+    assert [record] == list(fresh_db["t"].rows)
diff --git a/tests/test_suggest_column_types.py b/tests/test_suggest_column_types.py
index a392c09..e36c58f 100644
--- a/tests/test_suggest_column_types.py
+++ b/tests/test_suggest_column_types.py
@@ -21,6 +21,7 @@ from sqlite_utils.utils import suggest_column_types
         ([{"a": 1}, {"a": 1.1}], {"a": float}),
         ([{"a": b"b"}], {"a": bytes}),
         ([{"a": b"b"}, {"a": None}], {"a": bytes}),
+        ([{"a": "a", "b": None}], {"a": str, "b": str}),
     ],
 )
 def test_suggest_column_types(records, types):