问题是 1995 年和 1996 年有多少次采访。您必须使用 IN 关键字进行比较。还有一个名为 YEAR() 的函数将返回日期的年份部分。
桌子:
mysql> SELECT interviewdate "Date"
-> FROM interview;
+------------+
| Date |
+------------+
| 1995-06-01 |
| 1995-06-01 |
| 1995-06-30 |
| 1995-06-30 |
| 1995-07-01 |
| 1995-08-01 |
| 1995-08-01 |
| 1995-08-02 |
| 1995-12-01 |
| 1995-12-02 |
| 1995-12-04 |
| 1996-01-21 |
| 1996-02-01 |
| 1996-02-02 |
| 1996-07-01 |
| 1996-07-01 |
| 1996-08-01 |
| 1996-08-08 |
| 1996-08-11 |
| 1997-01-01 |
| 1997-01-01 |
| 1997-01-31 |
| 1997-02-01 |
| 1997-03-24 |
| 1997-03-31 |
| 1997-04-20 |
| 1997-04-22 |
| 1997-05-01 |
+------------+
28 rows in set (0.00 sec)
输出:
条件是仅将日期为 1995 和 1996 的那些计数到新表 AS“Count(*)”中。有谁知道如何做到这一点?我是 mySQL 的新手,并试图理解语法。我试过这样的事情:
SELECT interviewdate, COUNT(interviewdate) AS "COUNT(*)"
FROM interview
GROUP BY interviewdate
HAVING COUNT(interviewdate) == 1995 AND 1996;
+----------+
| COUNT(*) |
+----------+
| 19 |
+----------+
1 row in set (0.00 sec)