SQL CONVERT

The SQL CONVERT function is used to convert an expression from one data type to another. If the SQL Server CONVERT function is unable to change an expression into the desired data type, then it returns an Error. For this demonstration, we use the Employee table.

SQL CONVERT Function Syntax

The syntax of the SQL CONVERT Function

CONVERT (Data_Type [(Length)], Expression, [Style])

-- For example
SELECT CONVERT (VARCHAR(50), 245) AS [result_name]
FROM [Source]

• Data_Type: Specify the Data Type to which you want to convert an expression
• Length: It is an optional parameter of integer type. You can use this SQL Server parameter to specify the length of the target data type. By default, it is 30.
• Expression that you want to change into the desired data type using the SQL Convert function.
• Style: use this optional parameter of integer type to define the style.

SQL CONVERT Function to format Date

The list of formatting styles that are available in the SQL Server CONVERT function.

Without Century (yy)	With Century (yyyy)	Standard	Input/Output
–	0 to 100	This is the Default for both datetime, and smalldatetime	mon dd yyyy hh:miAM (or PM)
1	101	U.S.	1 = mm/dd/yy 101 = mm/dd/yyyy
2	102	ANSI	2 = yy.mm.dd 102 = yyyy.mm.dd
3	103	British/French	3 = dd/mm/yy 103 = dd/mm/yyyy
4	104	German	4 = dd.mm.yy 104 = dd.mm.yyyy
5	105	Italian	5 = dd-mm-yy 105 = dd-mm-yyyy
6	106	–	6 = dd mon yy 106 = dd mon yyyy
7	107	–	7 = Mon dd, yy 107 = Mon dd, yyyy
8	108	–	hh:mi:ss
–	9 or 109	Default + milliseconds	mon dd yyyy hh:mi:ss:mmmmAM (or PM)
10	110	USA	10 = mm-dd-yy 110 = mm-dd-yyyy
11	111	JAPAN	11 = yy/mm/dd 111 = yyyy/mm/dd
12	112	ISO	12 = yymmdd 112 = yyyymmdd
–	13 or 113	Europe Default + millisecond	dd mon yyyy hh:mi:ss:mmm(24h)
14	114	–	hh:mi:ss:mmm(24h)
–	20 or 120	ODBC canonical	yyyy-mm-dd hh:mi:ss(24h)
–	21 or 121	ODBC canonical with milliseconds. This is the Default for time, date, datetime2, and datetimeoffset	yyyy-mm-dd hh:mi:ss.mmm(24h)
–	126	ISO8601	yyyy-mm-ddThh:mi:ss.mmm (no Spaces)
–	127	ISO8601 with time zone Z	yyyy-mm-ddThh:mi:ss.mmmZ (no Spaces)
–	130	Hijri	dd mon yyyy hh:mi:ss:mmmAM
–	131	Hijri	dd/mm/yyyy hh:mi:ss:mmmAM

CONVERT Example to Format DATE

In this example, we use the SQL CONVERT function on GETDATE() to return the date in different formats.

SELECT CONVERT(VARCHAR(50), GETDATE()) AS 'Result 1';

SELECT CONVERT(VARCHAR(50), GETDATE(), 100) AS 'Result 2';
SELECT CONVERT(VARCHAR(50), GETDATE(), 101) AS 'Result 3';
 
SELECT CONVERT(VARCHAR(50), GETDATE(), 102) AS 'Result 4';
SELECT CONVERT(VARCHAR(50), GETDATE(), 103) AS 'Result 5';
 
SELECT CONVERT(VARCHAR(50), GETDATE(), 104) AS 'Result 6';
SELECT CONVERT(VARCHAR(50), GETDATE(), 105) AS 'Result 7';
SELECT CONVERT(VARCHAR(50), GETDATE(), 110) AS 'Result 8';

SQL CONVERT Money Format Example

If an expression is money or small money, then we can use the style argument to stylize. The list of money formatting styles that are available in the SQL Server CONVERT function.

Value	Output
0	It will only return two digits after the decimal point
1	It will separate every three digits by placing a comma. It will also return two digits after the decimal point.
2	This return four digits after the decimal point
126	This is equivalent to 2 when you are changing to char, or varchar

DECLARE @Sale MONEY
SET @Sale = 1234567.98723

SELECT CONVERT(VARCHAR(50), @Sale) AS 'Result 1';

SELECT CONVERT(VARCHAR(50), @Sale, 0) AS 'Result 2';

SELECT CONVERT(VARCHAR(50), @Sale, 1) AS 'Result 3';
SELECT CONVERT(VARCHAR(50), @Sale, 2) AS 'Result 4';

SELECT CONVERT(VARCHAR(50), @Sale, 256) AS 'Result 5';

SQL Convert float values Example

When an expression is float or real, we can use the style argument. The following are the formatting styles that are available in the SQL CONVERT function.

Value	Output
0	This return maximum of 6 digits
1	It returns eight digits. Always use in Scientific notation
2	It always returns 16 digits. Always use in Scientific notation
3	It is supported by SQL Server 2016. It returns 17 digits and is useful to perform the conversion without loosing

DECLARE @Sale FLOAT
SET @Sale = 1234567.98723

SELECT CONVERT(VARCHAR(50), @Sale) AS 'Result 1';

SELECT CONVERT(VARCHAR(50), @Sale, 0) AS 'Result 2';

SELECT CONVERT(VARCHAR(50), @Sale, 1) AS 'Result 3';
SELECT CONVERT(VARCHAR(50), @Sale, 2) AS 'Result 4';

SELECT CONVERT(VARCHAR(50), @Sale, 3) AS 'Result 5';

Convert Null Values Example

In this SQL convert function example, we will work with NULL values.

DECLARE @str AS VARCHAR(50)
SET @str = NULL

SELECT CONVERT(INT, @str) AS Result;

SELECT CONVERT(INT, NULL) AS Result;

If we use the SQL Convert function to change the ‘Tutorial Gateway’ string to date time. As you can see, it is not possible so, this function is returning Error as output.

SELECT CONVERT(INT, 'Tutorial Gateway') AS Result;

Execute the above Transact query

Msg 245, Level 16, State 1, Line 2
Conversion failed when converting the Varchar value 'Tutorial Gateway' to data type int.

In this SQLConvert Function example, we will apply this to our Employee table.

SELECT TOP 1000 [EmpID]
      ,[FirstName]
      ,[LastName]
      ,[Education]
      ,[Occupation]
      ,[YearlyIncome] AS [Yearly Income]
      ,CONVERT(VARCHAR(50),[Sales], 2) AS [Sale Amount]
      ,CONVERT(VARCHAR(50), [HireDate], 113) AS [Hire Date]
  FROM [Employee]