renato2099 commented on issue #1305:
URL:
https://github.com/apache/datafusion-python/issues/1305#issuecomment-3650913913
> The need to track the data frame names separately from the variable seems
unfortunate.
that is the case because of the way we are registering the dataframes with
the `SessionContext`
```
df1 = ctx.create_dataframe([[batch]], "l") # the dataframe is named "L"
when referenced
```
In the example, we are doing this because we need it to disambiguate columns
with the same name ... which is also our case 😅
> I'd like to instead do df.select(F.coalesce(df1.col("num"),
df2.col("num")).alias("num") unfortunately I don't think we currently have a
syntax like that (or a nice alternative) to dedup columns that have the same
name.
right, unfortunately datafusion-python doesn't support that syntax atm , but
that is a good feature request though
we can do the following though
```
import datafusion.functions as F
df6 = df3.select(
F.coalesce(col("l.num"), col("r.num")).alias("num"),
col("l.name"),
col("r.value"),
)
df6.show()
```
then we get
```
+-----+------+-------+
| num | name | value |
+-----+------+-------+
| 1 | a | true |
| 3 | c | true |
| 2 | b | |
| 5 | | false |
+-----+------+-------+
```
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