Validating if an expression is a date

Functions for Manipulating Data in SQL Server

Ana Voicu

Data Engineer

ISDATE(expression)

Determines whether an expression is a valid date data type

ISDATE() expression	Return type
date, time, datetime	1
datetime2	0
other type	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}

Sets the order of the date parts for interpreting strings as dates
Valid formats:
- 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}

Sets the language for the session
Implicitly sets the setting of SET DATEFORMAT
Valid languages: English, Italian, Spanish, etc.

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   |

Let's practice!

Functions for Manipulating Data in SQL Server