How can I check if a date is in range in MySQL?

Why do I get different results for this similar queries?

SELECT CASE WHEN CONCAT(2011, '-1-1') BETWEEN '2011-01-01' AND '2011-03-31' THEN 1 ELSE 0 END AS status;
+--------+
| status |
+--------+
|      0 |
+------开发者_如何转开发--+  

SELECT CASE WHEN CONCAT(2011, '-1-1') BETWEEN '2011-1-1' AND '2011-3-31' THEN 1 ELSE 0 END AS status;
+--------+
| status |
+--------+
|      1 |
+--------+

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Because you are comparing strings, not dates.

The easiest way to turn a string into a date is to wrap in DATE().

SELECT CASE WHEN DATE(CONCAT(2011, '-1-1'))
            BETWEEN DATE('2011-1-1') AND DATE('2011-3-31')
            THEN 1 ELSE 0 END AS status;

http://dev.mysql.com/doc/refman/5.0/en/datetime.html

You can also make your query shorter, since MySQL returns boolean as 1/0 natively.

SELECT DATE(CONCAT(2011, '-1-1'))
            BETWEEN DATE('2011-1-1') AND DATE('2011-3-31') as status;

---

You're comparing strings, not dates. Try explicitly casting to the desired datatype:

SELECT CASE WHEN CAST(CONCAT(2011, '-1-1') AS DATETIME) BETWEEN CAST('2011-01-01' AS DATETIME) AND CAST('2011-03-31' AS DATETIME) THEN 1 ELSE 0 END AS status;

---

Because it's doing a string comparison. You should use the mysl date function.

 SELECT CASE WHEN date(CONCAT(2011, '-1-1')) BETWEEN date('2011-1-1') AND date('2011-3-31') THEN 1 ELSE 0 END AS status;