尝试在SQL中删除尾随零时的语法错误

Question

To avoid cosmetic adjustments in the presentation layer, I need to remove trailing zeros from my data outputs - eg in my Hours column I need "2" as opposed to "2.000" or "18.5" as opposed to "18.500".

Having reviewed existing resources, I've come up with the following:

SELECT
  DATE_FORMAT(U.START_TIME + INTERVAL 1 hour, '%H:%i') as Start
, DATE_FORMAT(U.END_TIME + INTERVAL 1 hour, '%H:%i') as End
, CAST(CAST(TIMESTAMPDIFF(MINUTE, U.START_TIME, U.END_TIME)/60 as DECIMAL (6,2)) as FLOAT) as Hours
, REQUESTER_COMMENT as Requester_Commment
FROM VW_USER_SCHEDULE_INSTANCES U

I keep getting the error message:

Error Code: 1064. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FLOAT), REQUESTER_COMMENT as Requester_Comment

I'm struggling to work out what needs to be adjusted to avoid the error. Trying to integrate float is preventing any outputs. Apologies if I'm missing something obvious - I'm a total SQL beginner. Any assistance would be much appreciated!

Answer 1

You should get into the habit of reading the documentation for functions like CAST() . See https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html#function_cast

If you read the docs, you would learn that CAST() doesn't support FLOAT as a destination type. You can use BINARY, CHAR, DATE, DATETIME, DECIMAL, JSON, NCHAR, SIGNED INTEGER, TIME or UNSIGNED INTEGER. But not FLOAT or DOUBLE.

I suggest you try the ROUND() function. See https://dev.mysql.com/doc/refman/5.7/en/mathematical-functions.html#function_round

But my preferred answer is that you should use SQL for fetching raw data, and do formatting for a given presentation in your application code.

Answer 2

Just use to_seconds() :

SELECT DATE_FORMAT(U.START_TIME + INTERVAL 1 hour, '%H:%i') as Start,
       DATE_FORMAT(U.END_TIME + INTERVAL 1 hour, '%H:%i') as End,
       (TO_SECONDS(U.END_TIME) - TO_SECONDS(U.START_TIME)) / (60*60) as Hours,
       REQUESTER_COMMENT as Requester_Commment
FROM VW_USER_SCHEDULE_INSTANCES U;

You can format it however you like.