定义和用法
EXTRACT() 函数用于返回日期/时间的单独部分，比如年、月、日、小时、分钟等等。
语法
EXTRACT(unit FROM date)
date 参数是合法的日期表达式。unit 参数可以是下列的值：
| Unit 值 |
|---|
| MICROSECOND |
| SECOND |
| MINUTE |
| HOUR |
| DAY |
| WEEK |
| MONTH |
| QUARTER |
| YEAR |
| SECOND_MICROSECOND |
| MINUTE_MICROSECOND |
| MINUTE_SECOND |
| HOUR_MICROSECOND |
| HOUR_SECOND |
| HOUR_MINUTE |
| DAY_MICROSECOND |
| DAY_SECOND |
| DAY_MINUTE |
| DAY_HOUR |
| YEAR_MONTH |
实例
假设我们有如下的 "Orders" 表：
| OrderId | ProductName | OrderDate |
|---|---|---|
| 1 | Jarlsberg Cheese | 2008-11-11 13:23:44.657 |
下面是 SELECT 语句：
SELECT EXTRACT(YEAR FROM OrderDate) AS OrderYear,
EXTRACT(MONTH FROM OrderDate) AS OrderMonth,
EXTRACT(DAY FROM OrderDate) AS OrderDay,
FROM Orders
WHERE OrderId=1
结果如下所示：
| OrderYear | OrderMonth | OrderDay |
|---|---|---|
| 2008 | 11 | 11 |