Show empty string when date field is 1/1/1900

问题

I'm querying a database like so:

SELECT DISTINCT 
CASE WHEN CreatedDate = '1900-01-01 00:00:00.000' THEN '' ELSE CreatedDate END AS CreatedDate
FROM LitHoldDetails

lhd.CreatedDate is a DateTime field and is non-nullable. I want to display an empty string if the field is the minimum date (1/1/1900), but my CASE statement doesn't work; CreatedDate displays 1900-01-01 00:00:00.000 in my query when that value is in the database. I'm using SQL Server 2008 R2. What am I doing wrong?

回答1:

When you use a CASE expression (not statement) you have to be aware of data type precedence. In this case you can't just set a DATETIME to an empty string. Try it:

SELECT CONVERT(DATETIME, '');

One workaround is to present your date as a string:

CASE WHEN CONVERT(DATE, CreatedDate) = '1900-01-01' -- to account for accidental time
  THEN ''
  ELSE CONVERT(CHAR(10), CreatedDate, 120)
    + ' ' + CONVERT(CHAR(8), CreatedDate, 108)
END

Or you could fiddle with the presentation stuff where it belongs, at the presentation tier.

Here is an example that works exactly as you seem to want:

DECLARE @d TABLE(CreatedDate DATETIME);

INSERT @d SELECT '19000101' UNION ALL SELECT '20130321';

SELECT d = CASE WHEN CreatedDate = '19000101'
  THEN ''
  ELSE CONVERT(CHAR(10), CreatedDate, 120)
    + ' ' + CONVERT(CHAR(8), CreatedDate, 108)
END FROM @d;

Results:

d
-------------------
                    <-- empty string
2013-03-21 00:00:00

回答2:

select  ISNULL(CONVERT(VARCHAR(23), WorkingDate,121),'') from uv_Employee

回答3:

Try this code

(case when CONVERT(VARCHAR(10), CreatedDate, 103) = '01/01/1900' then '' else CONVERT(VARCHAR(24), CreatedDate, 121) end) as Date_Resolved

回答4:

Two nitpicks. (1) Best not to use string literals for column alias - that is deprecated. (2) Just use style 120 to get the same value.

    CASE 
      WHEN CreatedDate = '19000101' THEN '' 
      WHEN CreatedDate = '18000101' THEN '' 
      ELSE Convert(varchar(19), CreatedDate, 120)
    END AS [Created Date]

回答5:

An alternate solution that covers both min (1/1/1900) and max (6/6/2079) dates:

ISNULL(NULLIF(NULLIF(CONVERT(VARCHAR(10), CreatedDate, 120), '1900-01-01'), '2079-06-06'), '').

Whatever solution you use, you should do a conversion of your date (or datetime) field to a specific format to bulletproof against different default server configurations.

See CAST and CONVERT on MSDN: https://msdn.microsoft.com/en-us/library/ms187928.aspx

回答6:

Use this inside of query, no need to create extra variables.

CASE WHEN CreatedDate = '19000101' THEN '' WHEN CreatedDate =
'18000101' THEN ''  ELSE CONVERT(CHAR(10), CreatedDate, 120) + ' ' +
CONVERT(CHAR(8), CreatedDate, 108) END as 'Created Date'

Works like a charm.

来源：https://stackoverflow.com/questions/15554369/show-empty-string-when-date-field-is-1-1-1900

标签

sql-server

datetime

case