cast a varchar to date - sql

Question

i use a H2 database for a small project, all field are varchar
for a query, i must convert a string to date so i tried
SELECT * FROM USER WHERE cast(DATE_CONTRACT AS DATE) > '2005-02-21'
but there are an error
Code :
Error code 90009, SQL state 90009:
Cannot parse date constant
"2011-02-21-15.22.07", cause:
"java.lang.NumberFormatException: For
input string: ""21-15.22.07""";
any idea?
thanks

Answer 1

You have to use parsedatetime() in order to "cast" your character data to a date.
http://h2database.com/html/functions.html#parsedatetime
Something like this:
SELECT *
FROM USER
WHERE parsedatetime(DATE_CONTRACT, 'yyyy-MM-dd-HH.mm.ss') > DATE '2005-02-21'
Another good reason to never store dates, timestamps or numbers as character data

Answer 2

Of course you could use the built-in function PARSEDATETIME as follows:
CREATE TABLE USER(DATE_CONTRACT VARCHAR);
INSERT INTO USER VALUES('2011-02-21-15.22.07');
SELECT * FROM USER
WHERE PARSEDATETIME(DATE_CONTRACT, 'yyyy-MM-dd-HH.mm.ss') > DATE '2005-02-21';
But I guess it would make more sense to store the timestamp in a more standard format, so that no special parsing is required. Example:
CREATE TABLE USER(DATE_CONTRACT TIMESTAMP);
INSERT INTO USER VALUES('2011-02-21 15:22:07');
SELECT * FROM USER
WHERE DATE_CONTRACT > DATE '2005-02-21';
H2 supports the format supported by JDBC, plus ISO 8601.

Answer 3

Why convert to date? If DATE_CONTRACT uses a consistent CHAR(19), you can:
SELECT *
FROM USER
WHERE DATE_CONTRACT >= '2005-02-22-00.00.00'
;
Correct me if I'm wrong but if there is an index on DATE_CONTRACT, this will be faster than converting to date/datetime.