驗證運算式是否為日期

SQL Server 的資料操作函式

Ana Voicu

Data Engineer

ISDATE(expression)

判斷運算式是否為有效的日期型別

ISDATE() 運算式	回傳值
date、time、datetime	1
datetime2	0
其他型別	0

ISDATE(expression)

DECLARE @date1 NVARCHAR(20) = '2019-05-05'
DECLARE @date2 NVARCHAR(20) = '2019-01-XX'
DECLARE @date3 CHAR(20) = '2019-05-05 12:45:59.9999999'
DECLARE @date4 CHAR(20) = '2019-05-05 12:45:59'

SELECT
    ISDATE(@date1) AS valid_date,
    ISDATE(@date2) AS invalid_date,
    ISDATE(@date3) AS valid_datetime2,
    ISDATE(@date4) AS valid_datetime;

| valid_date | invalid_date |valid_datetime2 | valid_datetime |
|------------|--------------|----------------|----------------|
| 1          | 0            | 0              | 1              |

SET DATEFORMAT

SET DATEFORMAT {format}

設定剖析字串為日期時的日期部分順序
合法格式：
- mdy、dmy、ymd、ydm、myd、dym

SET DATEFORMAT

DECLARE @date1 NVARCHAR(20) = '12-30-2019'
DECLARE @date2 NVARCHAR(20) = '30-12-2019'

SET DATEFORMAT dmy;
SELECT
    ISDATE(@date1) AS invalid_dmy,
    ISDATE(@date2) AS valid_dmy;

|invalid_dmy| valid_dmy |
|-----------|-----------|
| 0         | 1         |

SET LANGUAGE

SET LANGUAGE {language}

設定目前工作階段的語言
隱性設定 SET DATEFORMAT 的行為
合法語言：English、Italian、Spanish 等

SET LANGUAGE

SET LANGUAGE English;
SELECT
    ISDATE('12-30-2019') AS mdy,
    ISDATE('30-12-2019') AS dmy;

| mdy | dmy |
|-----|-----|
| 1   | 0   |

SET LANGUAGE

SET LANGUAGE French;
SELECT
    ISDATE('12-30-2019') AS mdy,
    ISDATE('30-12-2019') AS dmy;

| mdy | dmy |
|-----|-----|
| 0   | 1   |

一起來練習吧！

SQL Server 的資料操作函式