from_second
description
Syntax
DATETIME FROM_SECOND(BIGINT unix_timestamp)
DATETIME FROM_MILLISECOND(BIGINT unix_timestamp)
DATETIME FROM_MICROSECOND(BIGINT unix_timestamp)
将时间戳转化为对应的 DATETIME，传入的是整型，返回的是DATETIME类型。若unix_timestamp < 0 或函数结果大于 9999-12-31 23:59:59.999999，则返回NULL。
example
mysql> set time_zone='Asia/Shanghai';
mysql> select from_second(-1);
+---------------------------+
| from_second(-1) |
+---------------------------+
| NULL |
+---------------------------+
mysql> select from_millisecond(12345678);
+----------------------------+
| from_millisecond(12345678) |
+----------------------------+
| 1970-01-01 11:25:45.678 |
+----------------------------+
mysql> select from_microsecond(253402271999999999);
+--------------------------------------+
| from_microsecond(253402271999999999) |
+--------------------------------------+
| 9999-12-31 23:59:59.999999 |
+--------------------------------------+
mysql> select from_microsecond(253402272000000000);
+--------------------------------------+
| from_microsecond(253402272000000000) |
+--------------------------------------+
| NULL |
+--------------------------------------+keywords
FROM_SECOND,FROM,SECOND,MILLISECOND,MICROSECOND