html_url,issue_url,id,node_id,user,user_label,created_at,updated_at,author_association,body,reactions,issue,issue_label,performed_via_github_app
https://github.com/simonw/sqlite-utils/issues/186#issuecomment-897600677,https://api.github.com/repos/simonw/sqlite-utils/issues/186,897600677,IC_kwDOCGYnMM41gEyl,9308268,rayvoelker,2021-08-12T12:32:14Z,2021-08-12T12:32:14Z,NONE,"Actually, I forgot to include the `bib_pub_year` in the extract ... 

But also, I tried again with empty string values instead of `NULL` values and it seems to place the foreign key properly / correctly... 

```python3
sql = """"""\
INSERT INTO ""circulation_info"" (""item_id"", ""bib_title"", ""bib_creator"", ""bib_format"", ""bib_pub_year"", ""checkout_date"")
VALUES
(1, ""title one"", ""creator one"", ""Book"", 2018, ""2021-08-12 00:01""),
(2, ""title two"", ""creator one"", ""Book"", 2019, ""2021-08-12 00:02""),
(3, ""title three"", """", ""DVD"", 2020, ""2021-08-12 00:03""),
(4, ""title four"", """", ""DVD"", """", ""2021-08-12 00:04""),
(5, ""title five"", """", ""DVD"", """", ""2021-08-12 00:05"")
""""""

with sqlite3.connect('test_bib_2.db') as con:
    con.execute(sql)
```

```python3
db[""circulation_info""].extract(
    [
        ""bib_title"",
        ""bib_creator"",
        ""bib_format"",
        ""bib_pub_year""
    ],
    table=""bib_info"", 
    fk_column=""bib_info_id""
)
```

```
{'id': 1, 'item_id': 1, 'bib_info_id': 1, 'bib_pub_year': 2018, 'checkout_date': '2021-08-12 00:01'}
{'id': 2, 'item_id': 2, 'bib_info_id': 2, 'bib_pub_year': 2019, 'checkout_date': '2021-08-12 00:02'}
{'id': 3, 'item_id': 3, 'bib_info_id': 3, 'bib_pub_year': 2020, 'checkout_date': '2021-08-12 00:03'}
{'id': 4, 'item_id': 4, 'bib_info_id': 4, 'bib_pub_year': '', 'checkout_date': '2021-08-12 00:04'}
{'id': 5, 'item_id': 5, 'bib_info_id': 5, 'bib_pub_year': '', 'checkout_date': '2021-08-12 00:05'}

---

{'id': 1, 'bib_title': 'title one', 'bib_creator': 'creator one', 'bib_format': 'Book'}
{'id': 2, 'bib_title': 'title two', 'bib_creator': 'creator one', 'bib_format': 'Book'}
{'id': 3, 'bib_title': 'title three', 'bib_creator': '', 'bib_format': 'DVD'}
{'id': 4, 'bib_title': 'title four', 'bib_creator': '', 'bib_format': 'DVD'}
{'id': 5, 'bib_title': 'title five', 'bib_creator': '', 'bib_format': 'DVD'}
```
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",722816436,.extract() shouldn't extract null values,
https://github.com/simonw/sqlite-utils/issues/186#issuecomment-897588624,https://api.github.com/repos/simonw/sqlite-utils/issues/186,897588624,IC_kwDOCGYnMM41gB2Q,9308268,rayvoelker,2021-08-12T12:13:25Z,2021-08-12T12:13:25Z,NONE,"I think I ran into an issue that's perhaps related with `extract()`

I have a case where I want to create a lookup table for all the related title data where there are possibly multiple null values in the related columns ....
```python3
sql = """"""\
INSERT INTO ""circulation_info"" (""item_id"", ""bib_title"", ""bib_creator"", ""bib_format"", ""bib_pub_year"", ""checkout_date"")
VALUES
(1, ""title one"", ""creator one"", ""Book"", 2018, ""2021-08-12 00:01""),
(2, ""title two"", ""creator one"", ""Book"", 2019, ""2021-08-12 00:02""),
(3, ""title three"", NULL, ""DVD"", 2020, ""2021-08-12 00:03""),
(4, ""title four"", NULL, ""DVD"", NULL, ""2021-08-12 00:04""),
(5, ""title five"", NULL, ""DVD"", NULL, ""2021-08-12 00:05"")
""""""

with sqlite3.connect('test_bib.db') as con:
    con.execute(sql)
```

when I run the `extract()` method ... 

```python3
db[""circulation_info""].extract(
    [
        ""bib_title"",
        ""bib_creator"",
        ""bib_format""        
    ],
    table=""bib_info"", 
    fk_column=""bib_info_id""
)

db = sqlite_utils.Database(""test_bib.db"")

for row in db[""circulation_info""].rows:
    print(row)

print(""\n---\n"")

for row in db[""bib_info""].rows:
    print(row)
```

results in this .. 
```
{'id': 1, 'item_id': 1, 'bib_info_id': 1, 'bib_pub_year': 2018, 'checkout_date': '2021-08-12 00:01'}
{'id': 2, 'item_id': 2, 'bib_info_id': 2, 'bib_pub_year': 2019, 'checkout_date': '2021-08-12 00:02'}
{'id': 3, 'item_id': 3, 'bib_info_id': None, 'bib_pub_year': 2020, 'checkout_date': '2021-08-12 00:03'}
{'id': 4, 'item_id': 4, 'bib_info_id': None, 'bib_pub_year': None, 'checkout_date': '2021-08-12 00:04'}
{'id': 5, 'item_id': 5, 'bib_info_id': None, 'bib_pub_year': None, 'checkout_date': '2021-08-12 00:05'}

---

{'id': 1, 'bib_title': 'title one', 'bib_creator': 'creator one', 'bib_format': 'Book'}
{'id': 2, 'bib_title': 'title two', 'bib_creator': 'creator one', 'bib_format': 'Book'}
{'id': 3, 'bib_title': 'title three', 'bib_creator': None, 'bib_format': 'DVD'}
{'id': 4, 'bib_title': 'title four', 'bib_creator': None, 'bib_format': 'DVD'}
{'id': 5, 'bib_title': 'title five', 'bib_creator': None, 'bib_format': 'DVD'}
```

Seems like it's correctly generating the row data for those lookups, but it's not correctly updating the foreign key back to the primary table? Looks like it just results in a `NULL` value in that original table.

Any ideas on why? Thanks again!","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",722816436,.extract() shouldn't extract null values,