日期值无效的Oracle案例声明

Question

I have the below case statement but I would like to add on to the case statement where END_DT is 1/1/3000 classify as Open.

CASE WHEN x.END_dt IS NOT NULL OR REASON IS NOT NULL 
THEN 'Closed' ELSE 'Open' END AS Enrolled

I'm getting the below results but in this case this should be classified as Open under the Enrolled column

I've tried adding to the Case Statment but I get errors.

One - inconsistent datatype; expected Date got number Two - When add '1/1/3000' to the date - Not a valid month.

Help would be appreciated.

Table

 id  End_dt          Reason  Enrolled
  1    1/1/3000               Closed

Answer 1

Thanks to mathguy for reminding me about the ANSI standard date format. I changed my example so assuming x.END_dt is a DATE datatype:

  CASE
    WHEN x.END_dt = date '3000-01-01'
      THEN 'Open'
    WHEN x.END_dt IS NULL AND REASON IS NULL
      THEN 'Open'
    WHEN x.END_dt IS NOT NULL OR REASON IS NOT NULL
      THEN 'Closed'
    ELSE 'Unexpected x.END_dt value: ' || to_char(x.END_dt)
  END AS Enrolled

I also tightened up the case statement to handle an unexpected END_dt value and explicitly test conditions on their own 'WHEN' lines. I like to do this as this way the intention of the test is clear, it's clear which expression is being testing when stepping through a debugger (like Toad), and when the clients inevitably want to change things its easy to move a line around or change the order of tests when they are on their own lines.

Answer 2

To avoid any reliance on NLS_DATE_FORMAT , one can use the ANSI standard date format (which is supported by Oracle): WHEN x.end_dt = date '3000-01-01' THEN ... . The whole CASE expression can be written like so:

CASE
  WHEN x.end_dt = date '3000-01-01' OR (x.end_dt IS NULL AND x.reason IS NULL)
    THEN 'Open'
  ELSE   'Closed'
END AS enrolled