HaoYang670 opened a new issue, #3569:
URL: https://github.com/apache/arrow-datafusion/issues/3569
**Describe the bug**
A clear and concise description of what the bug is.
**To Reproduce**
Steps to reproduce the behavior:
```
❯ select concat('a', null) from t;
+------------------------+
| concat(Utf8("a"),NULL) |
+------------------------+
| a |
+------------------------+
1 row in set. Query took 0.003 seconds.
❯ select 'a' || null from t;
+-------------------+
| Utf8("a") || NULL |
+-------------------+
| |
+-------------------+
1 row in set. Query took 0.003 seconds.
❯
```
**Expected behavior**
The two queries should return the same result.
In Spark, string_concat always return null when there is `null` element: (on
Spark3.3.0)
```scala
scala> df.selectExpr("'a' || null ").show
+---------------+
|concat(a, NULL)|
+---------------+
| null|
+---------------+
scala> df.selectExpr("concat('a' || null)").show
+-----------------------+
|concat(concat(a, NULL))|
+-----------------------+
| null|
+-----------------------+
```
**Additional context**
Add any other context about the problem here.
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