SQL date conversion for 8 char value with 00 as days

Question

I have been having trouble trying to figure out how to properly convert the data. In its current form it is varchar and the data is as follows:

19260200, 19770900, 20030400, 20120300, 20020500,

So as you can see I have the year and months, but have no values for dates. When I try to insert it into SQL field formatted as datetime i get errors. Anyone know how i can fix this? I am working with a DB of 700,000 records so I need to be able to write some code to address it and not just manually go through and change.

Thanks in advance for the help!!!

Answer 1

INSERT dbo.destination(date_column)
SELECT dt FROM 
(
  SELECT dt = CASE 
    WHEN src_date_column LIKE '%00' THEN 
      STUFF(src_date_column, 8, 1, '1') 
    ELSE src_date_column 
  END
  FROM dbo.source
) AS x
WHERE ISDATE(dt) = 1;

To address comments:

AS x is just an alias. A derived table needs to be called something. If you just say:

SELECT x FROM (SELECT x = 1);

You get this unhelpful error:

Msg 102, Level 15, State 1
Incorrect syntax near ';'.

But not if you say:

SELECT x FROM (SELECT x = 1) AS y;

As for your other question, you can simply add other columns to the inner SELECT, e.g.:

INSERT dbo.Citation(PatentNo, Citation, CitedBy, CitationDate)
SELECT PatentNo, Citation, WhoCitedThis, dt 
FROM 
(
  SELECT PatentNo, CitationSource, WhoCitedThis, dt = CASE
    WHEN CitationDate LIKE '%00' THEN STUFF(CitationDate, 8, 1, '1') 
    ELSE CitationDate 
  END 
  FROM dbo.CitationSource
) AS x
WHERE ISDATE(dt) = 1;

Now, you need to decide what you want to do with invalid dates, such as 20120231 or 20120399. Those are just left behind. My first recommendation would be to make that a proper date or datetime column, and reject bad dates from getting into the system in the first place.

Answer 2

You can try something like this:

cast(left(val, 6)+'01') as date)

That is, insert a valid day value into the string and do the conversion.