如何在MySQL中的DATETIME中从毫秒中删除尾随零

Question

How can I remove trailing zeros occurring in higher precision of DATETIME in MySQL.

Sample input/output:

2018-04-13 13:02:32.948000     =>    2018-04-13 13:02:32.948

Answer 1

Based on the MySQL-Doc there should be a "fsp" parameter for DATETIME-fields.

CREATE TABLE fractest( c1 TIME(2), c2 DATETIME(2), c3 TIMESTAMP(2) );

mysql> INSERT INTO fractest VALUES ('17:51:04.777', '2014-09-08 17:51:04.777', '2014-09-08 17:51:04.777');

mysql> SELECT * FROM fractest;
+-------------+------------------------+------------------------+
| c1          | c2                     | c3                     |
+-------------+------------------------+------------------------+
| 17:51:04.78 | 2014-09-08 17:51:04.78 | 2014-09-08 17:51:04.78 |
+-------------+------------------------+------------------------+

But it's not possible to remove trailing zeros dynamically you have to fix the length of the fractional seconds precision.

Source: Fractional Seconds in Time Values

Answer 2

If you output the DATETIME value with milliseconds directly MySQL removes the trailing zeros.

CREATE TABLE test (
    colDateTime DATETIME(6)
);

INSERT INTO test VALUES ('2018-04-17 11:12:13.444000');

Now we use the following SELECT statement:

SELECT * FROM test; -- output: 2018-04-17T11:12:13.444Z (0 at the end are removed by MySQL).

The only way you get the zeros at the end is using the DATE_FORMAT :

SELECT DATE_FORMAT(colDateTime, '%f') FROM test; -- output: 444000

In this case you can TRIM the zero of this string value:

SELECT TRIM(TRAILING '0' FROM DATE_FORMAT(colDateTime, '%Y-%m-%d %H:%i:%s.%f')) FROM test;

demo: http://sqlfiddle.com/#!9/b0655f/5/2