# DATEDIFF
#### 语法
```
INT DATEDIFF(VARCHAR enddate, VARCHAR startdate)
INT DATEDIFF(TIMESTAMP enddate, VARCHAR startdate)
INT DATEDIFF(VARCHAR enddate, TIMESTAMP startdate)
INT DATEDIFF(TIMESTAMP enddate, TIMESTAMP startdate)
```
#### 描述
DATEDIFF函数用于计算两个日期之间的天数差值。计算方式为enddate减去startdate，即返回值 = enddate - startdate。当enddate晚于startdate时返回正数，当enddate早于startdate时返回负数。
#### 约束与限制
本章节仅适用于MRS 3.6.0-LTS.1及之后版本。
#### 入参
| 参数        | 数据类型              |
|:---|:---|
| enddate   | TIMESTAMP、VARCHAR |
| startdate | TIMESTAMP、VARCHAR |
   
![](https://support.huaweicloud.com/cmpntguide-lts-mrs/public_sys-resources/note_3.0-zh-cn.png)
- VARCHAR日期格式：yyyy-MM-dd或yyyy-MM-dd HH:mm:ss。
- 如果入参中任何一个为NULL，则返回为NULL。
 
#### 示例
```
CREATE TABLE source (
  time1 TIMESTAMP
) WITH (
  'connector' = 'datagen',
  'rows-per-second' = '1'
);
create TABLE print with(
'connector' = 'print'
)as select 
DATEDIFF('2025-10-15 00:00:00', '2025-9-15 00:00:00') as int1, 
        DATEDIFF(time1 ,'2025-12-1 00:00:00') as int2, 
        DATEDIFF('2025-12-1',time1 ) as int3, 
        DATEDIFF(time1 ,CAST(null as VARCHAR)) as int4, 
        DATEDIFF(CAST(null as VARCHAR), '2025-12-1 00:00:00') as int5, 
        DATEDIFF(CAST(null as VARCHAR), time1 ) as int6, 
        DATEDIFF(time1 ,time1 )as int7
from source;
```
表1返回结果 
| **int1(INT)** | **int2(INT)** | **int3(INT)** | **int4(INT)** | **int5(INT)** | **int6(INT)** | **int7(INT)** |
|:---|:---|:---|:---|:---|:---|:---|
| 30            | 49            | -49           | null          | null          | null          | 0             |