snuyanzin commented on code in PR #25874:
URL: https://github.com/apache/flink/pull/25874#discussion_r1905081855
##########
flink-python/pyflink/table/expressions.py:
##########
@@ -350,14 +350,21 @@ def temporal_overlaps(left_time_point,
def date_format(timestamp, format) -> Expression:
"""
Formats a timestamp as a string using a specified format.
- The format must be compatible with MySQL's date formatting syntax as used
by the
- date_parse function.
- For example `date_format(col("time"), "%Y, %d %M")` results in strings
formatted as
- "2017, 05 May".
+ Supported functions:
+ 1. date_format(TIMESTAMP, STRING) -> STRING
+ Converts timestamp to a string, using a format string.
+ The format string is compatible with Java's DateTimeFormatter.
+ 2. date_format(STRING, STRING) -> STRING
+ Converts timestamp string, using a format string.
+ The format string is compatible with Java's SimpleDateFormat.
+
+ Example:
+ ::
+
+ >>> table.select(date_format(to_timestamp('2020-04-15'), "yyyy/MM/dd"))
+ >>> table.select(date_format("2020-04-15", "MM/dd/yyyy"))
Review Comment:
IIUC it works only with timestamp string like
```sql
SELECT date_format('2020-04-15 12:12:12', 'MM/dd/yyyy');
```
and for the expression from this PR like
```python
table.select(date_format("2020-04-15", "MM/dd/yyyy"))
```
it will return `null`
I think it is better to provide examples which could return some meaningful
output
WDYT?
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