How to query a column with an awkward date format

Question

Here is how the date is formatted:

 XXXXXX001221

This date is for Dec 21

If I want to get yesterdays entries using the CURDATE() function how would I do this?

Answer 1

If you're just doing month-day (indices are based on the string format of CURDATE(), which is YYYY-MM-DD):

SELECT * FROM table_name
WHERE date_field LIKE
  CONCAT('%', SUBSTR(DATE_SUB(CURDATE(), INTERVAL 1 DAY) FROM 6 FOR 2),
              SUBSTR(DATE_SUB(CURDATE(), INTERVAL 1 DAY) FROM 9 FOR 2));

Or an alternative way using EXTRACT():

SELECT * FROM table_name
WHERE date_field LIKE
  CONCAT('%', EXTRACT(MONTH FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)),
              EXTRACT(DAY FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)));

For year as well:

SELECT * FROM table_name
WHERE date_field LIKE
  CONCAT('%', SUBSTR(DATE_SUB(CURDATE(), INTERVAL 1 DAY) FROM 3 FOR 2),
              SUBSTR(DATE_SUB(CURDATE(), INTERVAL 1 DAY) FROM 6 FOR 2),
              SUBSTR(DATE_SUB(CURDATE(), INTERVAL 1 DAY) FROM 9 FOR 2));


SELECT * FROM table_name
WHERE date_field LIKE
  CONCAT('%', EXTRACT(YEAR FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)),
              EXTRACT(MONTH FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)),
              EXTRACT(DAY FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)));

EDIT: Instead of WHERE date_field LIKE ... you can use WHERE RIGHT(date_field, 6) = ... as mentioned in codethis' answer:

SELECT * FROM table_name
WHERE RIGHT(date_field, 4) =
  CONCAT(EXTRACT(MONTH FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)),
         EXTRACT(DAY FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)));

SELECT * FROM table_name
WHERE RIGHT(date_field, 6) =
  CONCAT(EXTRACT(YEAR FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)),
         EXTRACT(MONTH FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)),
         EXTRACT(DAY FROM DATE_SUB(CURDATE(), INTERVAL 1 DAY)));

NOTE: You can also use a variable to save calculating DATE_SUB(CURDATE(), INTERVAL 1 DAY) all the time.

SET @yesterday = DATE_SUB(CURDATE(), INTERVAL 1 DAY);
SELECT ...

Answer 2

Try something like:

SELECT * FROM table WHERE RIGHT(date_col, 6) = (SELECT CONVERT(VARCHAR(6), GETDATE()-1, 12) AS [YYMMDD])