将日期转换为数字数据类型

Question

I am trying to convert date to number like below, not sure which function works better.

Database used is SQL Server.

Table details

create table test 
(
    id varchar(255),
    call_date varchar(255)
);

insert into test('26203', '14-Aug-2020');

I need output as 4405726203 -- its concatenation of date ( 14-Aug-2014 ) + id ( 26203 )

Answer 1

This is too long for a comment.

SQL Server allows you to convert a datetime to a float. That would be:

select cast(dte as float)
from (values (convert(datetime, '14-Aug-2020'))) v(dte)

However, the corresponding floating point value is 44055 ( https://dbfiddle.uk/?rdbms=sqlserver_2019&fiddle=d142a64db0872e7572eb4fbd6d5d5fe7 ). It is a bit of mystery what your intention is.

You could subtract 2, but that seems arbitrary. You could calculate the number of days since 1899-12-30. But that also seems arbitrary.

In any case, once you figure out how to convert the date to the number you want, just use concat() to combine the values.

Answer 2

我找到了解决方案：

convert(varchar,CAST(CONVERT(datetime,call_date) as bigint)) + id

Answer 3

Under the hood, a SQL Server DateTime is a tuple of 2 32-bit integers:

• The first integer is a count of days since since the epoch, which for SQL Server is 1 January 1900
• The second integer is a count of milliseconds since start of day ( 00:00:00.000 ). Except that the count ticks up in 3- or 4-milliscond increments. Microsoft only knows why that decision was made.

You can get the count of days since the epoch with

convert( int, convert( date, t.call_date ) )

[wrap that in convert(varchar, ... ) to turn it into a string]

Looks like your id is already a varchar , so you can say:

select compound_key = convert(varchar,
                        convert(int,
                          convert(date,
                            call_date
                          )
                        )
                      )
                    + t.id
from test t

I would suggest padding both fields with leading zeros to a fixed length so as to avoid possible collisions (assuming you're trying to generate a key here). Signed 32-bit integer overflows a 2.1 billion-ish, so 9 digits for each field is sufficient.

Answer 4

This works

select concat(datediff(d, 0, cast(call_date as date)), id)
from 
  (values ('26203','14-Aug-2020')) v(id, call_date);

Results

4405526203