Question

Query 1 works but query 2 doesn’t:

Query #1:

SELECT * FROM `users` WHERE users.dob <= '1994-1-14' AND users.dob >= '1993-1-14' LIMIT 10

Query #2:

SELECT * FROM `users` WHERE users.dob BETWEEN '1994-1-14' AND '1993-1-14' LIMIT 10

The 2nd one should be able to do the same thing as the first but I don’t understand why it’s not working.

The dob (date of birth) field in the users table is a type date field with records that look like this:

1988-11-08  
1967-11-14  
1991-03-09      
1958-03-08  
1967-06-30  
1988-10-19   
1986-01-23  
1965-09-20

YEAR – MONTH – DAY

With either query #1 or #2 I’m trying to get back all users who are between 18 and 19 years of age, because 1994-1-14 is exactly 18 years from today and 1993-1-14 is 19 years from today. So is there a way to get the between query to work?

By not working I mean it doesn’t return any records from the db while the working query does.

Also is the between query more efficient or is the performance difference negligible?

Answer 1

The usage is wrong. See the BETWEEN documentation:

expr BETWEEN min AND max is equivalent to (min <= expr AND expr <= max).

Therefore, users.dob BETWEEN '1994-1-14' AND '1993-1-14' is the same as ('1994-1-14' <= users.dob AND users.dob <= '1993-1-14'), of which there will never be more than 0 results.

Simply reverse the order 🙂

There will be no performance difference when using either form, possibly subject to the note below. This transformation happens at the query planner level. However, if you have concerns, remember to profile, profile, profile. Then you can see for yourself and appease the premature-optimization demons.

---

Also note the … note:

For best results when using BETWEEN with date or time values, use CAST() to explicitly convert the values to the desired data type.