Oracle 19c - 零填充年

Question

I have some zero padded year DATE column values (eg 0018-04-30), but not all values. Most are 4 digit years (eg 2022). What's the most efficient way of converting to a year with century (ie 2018-04-30).

I'm not a Oracle guy, but what I came up with is to use a CASE statement with EXTRACT and ADD_MONTHS functions:

CASE 
    WHEN EXTRACT(YEAR FROM DateColumn) < 1000 THEN ADD_MONTHS(DateColumn,(12*2000)) 
    ELSE DateColumn 
END

Example:

SELECT
    TO_CHAR(
        CASE 
            WHEN EXTRACT(YEAR FROM (DATE '18-04-30')) < 1000 THEN ADD_MONTHS((DATE '18-04-30'),(12*2000)) 
            ELSE (DATE '18-04-30') 
        END,'YYYY-MM-DD') AS CorrectedDate
FROM DUAL ;

Is there a better, more efficient, way of doing this?

Answer 1

Use an INTERVAL literal to add 2000 years to your dates:

SELECT dt + INTERVAL '2000' YEAR(4)
  FROM DATE_TABLE

db<>fiddle here

Also, your CASE expression can be a bit simpler:

CASE 
  WHEN DateColumn < DATE '1000-01-01' THEN DateColumn + INTERVAL '2000' YEAR(4)
  ELSE DateColumn 
END

Answer 2

You may remove leading zeroes from the date using ltrim function and use RR date format element to convert the result to a date, which was introduced for y2k problem (I presume this is the source of such dates):

 with dates(dt) as ( select * from sys.odcidatelist( date '0018-04-30', date '3018-05-30', date '0070-12-29' ) ) select to_date( ltrim(to_char(dt, 'yyyy-mm-dd'), '0'), 'rr-mm-dd' ) as dt from dates;

|  DT | 
|  :--------- | 
|  2018-04-30 | 
|  3018-05-30 | 
|  1970-12-29 | 

db<>fiddle here