xuzifu666 commented on code in PR #4306:
URL: https://github.com/apache/calcite/pull/4306#discussion_r2045894208
##########
core/src/main/java/org/apache/calcite/sql/dialect/MysqlSqlDialect.java:
##########
@@ -366,17 +369,39 @@ private static void unparseFloor(SqlWriter writer,
SqlCall call) {
case SECOND:
format = "%Y-%m-%d %H:%i:%s";
break;
+ case MILLISECOND:
+ needSubStr = true;
+ format = "%Y-%m-%d %H:%i:%s.%f";
+ substringLength = 23;
Review Comment:
Hi @mihaibudiu , thanks for the suggestion, do you mean only use date_format
to archive it?
According to my previous research, currently MySQL can only extract
microsecond by this way:
```
SELECT microsecond(NOW(6));
>953213
```
but seem there is no other way to extract millisecond：
```
SELECT MILLISECOND(NOW(6));
>[42000]: FUNCTION test_db.MILLISECOND does not exist
```
and seems no other way to get MILLISECOND directly.
I also test trailing zeros in fractional part:
```
select DATE_FORMAT(NOW(6), '%Y-%m-%d %H:%i:%s.000');
>2025-04-16 10:44:35.000
select DATE_FORMAT(NOW(6), '%Y-%m-%d %H:%i:%s.%f000');
>2025-04-16 10:45:10.467580000
```
%f can only get six digits because MySQL max precision is 6.
But according as I know users just use this way(substr + dateformat) to get
millisecond/microsecond as a universal solution in many real production
practice.
WDYT?
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