When Mysql compares two different data types, the first step is to convert them into the same type and then compare. So when comparing Date and String, must String be converted into Date? The answer is Yes. http://dev.mysql.com/doc/refman/5.0/en/type-conversion.html If one of the arguments is a TIMESTAMP or DATETIME column and the other argument is a constant, the constant is converted to a timestamp before the comparison is performed.
For a simple example, if string comparison is used, the string "2004-04-31" should be larger than the date 2004-01-01, but 4-31 is an invalid date (April is smaller month), will be converted to "0000-00-00", so 2004-01-01 (date) > "2014-04-31".
Mysql documentation on Date type http://dev.mysql.com/doc/refman/5.5/en/datetime.html
There is a passage like this: invalid dates such as '2004-04-31' are converted to '0000-00-00' and a warning is generated. With strict mode enabled, invalid dates generate an error.
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When Mysql compares two different data types, the first step is to convert them into the same type and then compare. So when comparing Date and String, must String be converted into Date? The answer is Yes.
http://dev.mysql.com/doc/refman/5.0/en/type-conversion.html
If one of the arguments is a TIMESTAMP or DATETIME column and the other argument is a constant, the constant is converted to a timestamp before the comparison is performed.For a simple example, if string comparison is used, the string "2004-04-31" should be larger than the date 2004-01-01, but 4-31 is an invalid date (April is smaller month), will be converted to "0000-00-00", so 2004-01-01 (date) > "2014-04-31".
Mysql documentation on Date type
http://dev.mysql.com/doc/refman/5.5/en/datetime.html
There is a passage like this:
invalid dates such as '2004-04-31' are converted to '0000-00-00' and a warning is generated. With strict mode enabled, invalid dates generate an error.