Zero length string value converts to <NA>

[StpMax]

If i do:

df = pd.DataFrame([['a', '']], columns=['a','b'])
dfsql.sql_query('select * from df', df=df)

then i get:

   a     b
0  a  <NA>

[StpMax]

also sql_query returns wrong result if use empty string as filter:

df = pd.DataFrame([['a', '']], columns=['a','b'])
dfsql.sql_query("select * from df where b = ''", df=df)

result is Empty DataFrame

[tomhuds]

@StpMax can we archive this project? or close issue?