SQL 2012: Let’s Make a Date with DATEFROMPARTS and TRY_PARSE!

Aug 9, 2012 / By Chris Presley

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Continuing on from my last post, I felt like cleaning up some more data and using more SQL Server 2012 features. I happened on DATEFROMPARTS on MSDN and felt like playing with it.

Often when moving data between systems, we’ll receive data in formats that need to be converted to be properly stored and used. I see a lot of value in the new DATEFROMPARTS feature.

First, we need to create a table and get some sample data to play with. We can do so with the following code:

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[tblDateTime]’) AND type in (N’U’))
DROP TABLE [dbo].[tblDateTime]
GO

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[tblDateTimeToConvert]’) AND type in (N’U’))
DROP TABLE [dbo].tblDateTimeToConvert
GO

Create table tblDateTimeToConvert (
col1 varchar(9) null)

Create table tblDateTime (
DT datetime null)
GO

— Populate with sample data

Insert into tblDateTimeToConvert Values
(‘19660612′),
(‘19881220′),
(‘19821115′),
(‘19851010′),
(‘19690213′),
(‘197/10526′),
(‘19730601′),
(‘19760117′),
(‘197 70924′),
(‘19790713′),
(‘19760811′),
(‘19710113′),
(‘19640126′),
(‘19710121′),
(‘19730″422′),
(‘19631026′),
(‘1954 0924′),
(‘19810807′),
(‘19791228′),
(‘19720323′),
(‘19780507′),
(‘19570124′),
(‘19860402′),
(‘19670217′),
(‘19830607′)

This code will create two tables: one to store our sample “dates” and one to insert the correctly converted date data into. Our sample data will be stored in tblDateTimeToConvert as character data in the format YYYYMMDD. To make things a bit more interesting, rather then inserting the straight numbers, I’ve added some “junk” characters and steps to fix them.

After the table is populated, you can view it with a simple select query: Select * from tblDateTimeToConvert.

If you’re lucky, your data will be uniform. I’m rarely that lucky so I’ve laced the data with junk. I tend to look at the data for patterns, then write code to clean it up. I started simply with:

Select *
from tblDateTimeToConvert
where ISNUMERIC(col1) = 0

…which returns 4 records.

So let’s clean the data up using Replace.

– Remove the slashes
Update tblDateTimeToConvert
Set Col1 = replace(col1, ‘/’, ”)
where col1 like ‘%/%’

— Remove the spaces
Update tblDateTimeToConvert
Set Col1 = replace(col1, ‘ ‘, ”)
where col1 like ‘% %’

— Remove the double quote
Update tblDateTimeToConvert
Set Col1 = replace(col1, ‘”‘, ”)
where col1 like ‘%”%’

This isn’t necessarily the most efficient way of searching and cleaning up the data, but it works. Now that our data is clean, let’s look at the “old” way I would have used to populate the table.

– Look at the data:

Select Convert(date, (left(col1, 4) + ‘-‘ + substring(col1, 5, 2) + ‘-‘ + right(col1, 2)))
from tblDateTimeToConvert

— Insert the Data
INSERT INTO [dbo].[tblDateTime] ([DT])
Select Convert(date, (left(col1, 4)+ ‘-‘ + substring(col1, 5, 2) + ‘-‘ + right(col1, 2)))
from tblDateTimeToConvert

Now, there’s nothing wrong with doing the conversion this way. The brackets can get confusing when you add in time, but it works.

Using DATEFROMPARTS, we can produce our converted date like this:

– Look at the data
Select DATEFROMPARTS(left(col1, 4), substring(col1, 5, 2), right(col1, 2))
From tblDateTimeToConvert

–Insert it
INSERT INTO [dbo].[tblDateTime] ([DT])
Select DATEFROMPARTS(left(col1, 4), substring(col1, 5, 2), right(col1, 2))
From tblDateTimeToConvert

Now that’s all fine and dandy, but in reading further on MSDN, we also get the new PARSE (and TRY_PARSE) statements. I decided to play with it. I realize this isn’t necessarily the intended use, but just for fun, what would those statements look like?

First off, I tried this:

Select try_parse(col1 as datetime)
from tblDateTimeToConvert

It didn’t work. Instead, it returned an error when using PARSE and NULLs with TRY_PARSE, so I knew something was up. I decided to actually read about the command and fed it my chopped up date, which worked to convert the data.

– Review the data
Select col1, TRY_Parse(left(col1, 4) + ‘-‘ + substring(col1, 5, 2) + ‘-‘ + right(col1, 2) as datetime2)
from tblDateTimeToConvert

–Insert the data
INSERT INTO [dbo].[tblDateTime] ([DT])
Select TRY_Parse(left(col1, 4) + ‘-‘ + substring(col1, 5, 2) + ‘-‘ + right(col1, 2) as datetime2)
from tblDateTimeToConvert

And there you have it!

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