jonahgao commented on issue #14112:
URL: https://github.com/apache/datafusion/issues/14112#issuecomment-2589171284
This is disallowed by #12608, because its output schema contains duplicate
names and can lead to ambiguous references.
Postgres also does not allow self-join unless a different table alias is
specified.
```sh
psql (16.6 (Ubuntu 16.6-0ubuntu0.24.04.1))
Type "help" for help.
psql=> select * from t1 cross join t1;
ERROR: table name "t1" specified more than once
psql=> select * from t1 cross join t1 t2;
a | b | a | b
---+---+---+---
1 | 1 | 1 | 1
(1 row)
```
I think we can add an `alias()` method for `DataFrame`. Similar to
[pyspark.sql.DataFrame.alias](https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.DataFrame.alias.html#)
```rust
impl DataFrame {
pub fn alias(self, alias: impl Into<TableReference>) -> Result<DataFrame> {
let plan =
LogicalPlanBuilder::from(self.plan).alias(alias)?.build()?;
Ok(DataFrame {
session_state: self.session_state,
plan,
})
}
}
```
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