Question

I have a table which is populated with data from an external source. The problem is I am getting two different format of dates for the same column, there are some records in '%Y-%m-%d %H:%i' format and other in '%Y-%d-%m %H:%i%s' format and they are all VARCHAR type.

I know how to convert a string type date field to a date/datetime field but how do I handle discrepancies in the way the dates are coming? Is it possible to Update dates on the basis of their individual format, so that I can apply a WHERE condition for updates to take place ONLY WHERE date_field is of '%Y-%m-%d %H:%i' format, and then another query to make updates for date field in '%Y-%d-%m %H:%i%s' format?

Right now when I try updating the tables with a common query I get error for the fields which donot match the format:

UPDATE my_table 
SET my_date_field = STR_TO_DATE(my_date_field,'%Y-%m-%d %H:%i:%s');

RESPONSE: Error Code: 1411. Incorrect datetime value: ’10-22-12 15:00′ for function str_to_date

UPDATE my_table 
SET my_date_field = STR_TO_DATE(my_date_field,'%Y-%d-%m %H:%i');

RESPONSE: Error Code: 1292. Truncated incorrect datetime value: ‘2010-01-01 00:00:00’

Answer 1

for this value 10-22-12 15:00 you should use, %y-%d-%m %H:%i

while for 2010-01-01 00:00:00, it should be %Y-%m-%d %H:%i:%s

so your query will use CASE

UPDATE my_table 
SET my_date_field = (CASE WHEN CHAR_LENGTH(my_date_field) = 14 
                          THEN STR_TO_DATE(my_date_field,'%y-%d-%m %H:%i')
                          ELSE STR_TO_DATE(my_date_field,'%Y-%m-%d %H:%i:%s')
                      END)

• See SQLFiddle Demo

Other Source

• DATE Formats