SQL Server sort by date

Question

I have a table of transactions in SQL Server 2016 with a column called mthweekyr where each row in this column has as a string, the month number, week number of the month, and year of the transaction, where week number is determined by day of the month / 7.

For example, if the transaction date was: 2018-09-28 , this would appear as 9-4-2018 .

The problem is that the original transaction date column is not actually in the table, and I would like to sort these transactions by the mthweekyr column, but am unable to do so because this column is not a date type, it is a string type. (I don't make the tables, I just use them!)

Any suggestions on how to proceed?

Thanks.

Answer 1

Here's another way...

declare @table table(mthweekyr varchar(10))
insert into @table
values
('9-4-2018'),
('8-4-2018'),
('9-5-2018'),
('7-5-2018'),
('7-4-2018'),
('9-5-2017'),
('9-4-2017')

select *
from @table
order by
    cast(right(mthweekyr,4) as int)                          --order by year first
    ,cast(left(mthweekyr,charindex('-',mthweekyr)-1) as int) --order by month. Works for single or double digit months
    ,left(right(mthweekyr,6),1)                              --order by week number which is always a single digit, since it's the week number of the month not the year.

Answer 2

Late answer , but perhaps a thinner alternative.

You can simply use the implicit conversion of mdy to date

Example

declare @table table(mthweekyr varchar(10))
insert into @table
values
('9-4-2018'),
('8-4-2018'),
('9-5-2018'),
('7-5-2018'),
('7-4-2018'),
('9-5-2017'),
('9-4-2017'),
('10-4-2017'),  -- added 2 digit month
('10-5-2017')   -- added 2 digit month

Select *
 From  @table
 Order By convert(date,mthweekyr)

Returns

mthweekyr
9-4-2017
9-5-2017
10-4-2017
10-5-2017
7-4-2018
7-5-2018
8-4-2018
9-4-2018
9-5-2018

Answer 3

Using JNevill's suggestion you could leverage PARSENAME for this.

declare @Date varchar(20) = '9-4-2018'
select PARSENAME(replace(@Date, '-', '.'), 1) + '-' + right('00' + PARSENAME(replace(@Date, '-', '.'), 3), 2) + '-' + right('00' + PARSENAME(replace(@Date, '-', '.'), 2), 2)

This returns 2018-09-04

You could also do some string manipulation but that starts to get rather tedious.

Answer 4

obviously not the most efficient I'm sure but to brute force it...

order by substring(@theStr, len(@theStr) - 4 + 1, 4)  
                + substring(@thestr,  charindex('-',@Thestr)+1,1)
                + right('00' + substring(@thestr, 1, charindex('-',@Thestr)-1),2)

here's how to get there by pieces:

declare @thestr varchar(255) = '9-4-2018'

Declare @SortStr as Varchar(255)

--year
Select @SortStr = substring(@theStr, len(@theStr) - 4 + 1, 4) 
print @Sortstr
--day
Select @SortStr = right('00' + substring(@thestr, 1, charindex('-',@Thestr)-1),2)
print @sortStr

--week
Select @SortStr = substring(@thestr,  charindex('-',@Thestr)+1,1)
print @sortStr

Select @SortStr = substring(@theStr, len(@theStr) - 4 + 1, 4)  
                + substring(@thestr,  charindex('-',@Thestr)+1,1)
                + right('00' + substring(@thestr, 1, charindex('-',@Thestr)-1),2)

will yield this output

2018
09
4
2018409

Answer 5

Since you know what the algorithm for date hashing is you can restore the original dates into a new column and then sort on it. Something like:

SELECT *, CONVERT(datetime2(1), 
    RIGHT(@mthweekyr, 4) + '-' + 
    LEFT(@mthweekyr, CHARINDEX('-', @mthweekyr) - 1) + '-' + 
    SUBSTRING(@mthweekyr, CHARINDEX('-', @mthweekyr) + 1, 
        CHARINDEX('-', @mthweekyr, CHARINDEX('-', @mthweekyr) + 1)
            - CHARINDEX('-', @mthweekyr) - 1)) AS EstimatedDate
FROM theTable
ORDER BY EstimatedDate

UPDATE

So the above is the long, harder way.

A smarter approach would be to leave the heavy lifting to the SQL Engine and use the third parameter of the CONVERT function , which specifies the style of the input. As the mthweekyr basically represents a USA style of mm-d-yyyy , the query will look like:

    SELECT *, CONVERT(datetime2(1), mthweekyr, 110) AS EstimatedDate
    FROM theTable
    ORDER BY EstimateDate