CAST and CONVERT (Transact-SQL)

**APPLIES TO:** SQL Server (starting with 2008) Azure SQL Database Azure SQL Data Warehouse Parallel Data Warehouse

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These functions convert an expression of one data type to another.

Example: Change the input datatype

Cast

SELECT 9.5 AS Original, CAST(9.5 AS int) AS int, 
    CAST(9.5 AS decimal(6,4)) AS decimal;

Convert

SELECT 9.5 AS Original, CONVERT(int, 9.5) AS int, 
    CONVERT(decimal(6,4), 9.5) AS decimal;

Here is the result set.
|Original |int |decimal |
|—-|—-|—-|
|9.5 |9 |9.5000 |

See the examples later in this topic.

Transact-SQL Syntax Conventions

Syntax

-- CAST Syntax:  
CAST ( expression AS data_type [ ( length ) ] )  
  
-- CONVERT Syntax:  
CONVERT ( data_type [ ( length ) ] , expression [ , style ] )  

Arguments

expression
Any valid expression.

data_type
The target data type. This includes xml, bigint, and sql_variant. Alias data types cannot be used.

length
An optional integer that specifies the length of the target data type. The default value is 30.

style
An integer expression that specifies how the CONVERT function will translate expression. For a style value of NULL, NULL is returned. data_type determines the range.

Return types

Returns expression, translated to data_type.

Date and Time Styles

For a date or time data type expression, style can have one of the values shown in the following table. Other values are processed as 0. Beginning with SQL Server 2012 (11.x) the only styles supported, when converting from date and time types to datetimeoffset, are 0 or 1. All other conversion styles return error 9809.

[!NOTE]
SQL Server supports the date format, in Arabic style, with the Kuwaiti algorithm.

¹ These style values return nondeterministic results. Includes all (yy) (without century) styles and a subset of (yyyy) (with century) styles.

² The default values (0 or 100, 9 or 109, 13 or 113, 20 or 120, and 21 or 121) always return the century (yyyy).

³ Input when you convert to datetime; output when you convert to character data.

⁴ Designed for XML use. For conversion from datetime or smalldatetime to character data, see the previous table for the output format.

⁵ Hijri is a calendar system with several variations. SQL Server uses the Kuwaiti algorithm.

[!IMPORTANT] By default, SQL Server interprets two-digit years based on a cutoff year of 2049. That means that SQL Server interprets the two-digit year 49 as 2049 and the two-digit year 50 as 1950. Many client applications, including those based on Automation objects, use a cutoff year of 2030. SQL Server SQL Server provides the two digit year cutoff configuration option to change the cutoff year used by SQL Server SQL Server SQL Server This allows for the consistent treatment of dates. We recommend specifying four-digit years.

⁶ Only supported when casting from character data to datetime or smalldatetime. When casting character data representing only date or only time components to the datetime or smalldatetime data types, the unspecified time component is set to 00:00:00.000, and the unspecified date component is set to 1900-01-01.

⁷Use the optional time zone indicator Z to make it easier to map XML datetime values that have time zone information to SQL Server datetime values that have no time zone. Z indicates time zone UTC-0. The HH:MM offset, in the + or - direction, indicates other time zones. For example: 2006-12-12T23:45:12-08:00.

When converting smalldatetime to character data, the styles that include seconds or milliseconds show zeros in these positions. When converting from datetime or smalldatetime values, use an appropriate char or varchar data type length to truncate unwanted date parts.

When converting character data to datetimeoffset, using a style that includes a time, a time zone offset is appended to the result.

float and real styles

For a float or real expression, style can have one of the values shown in the following table. Other values are processed as 0.

money and smallmoney styles

For a money or smallmoney expression, style can have one of the values shown in the following table. Other values are processed as 0.

xml styles

For an xml expression, style can have one of the values shown in the following table. Other values are processed as 0.

Binary styles

For a binary(n), char(n), varbinary(n), or varchar(n) expression, style can have one of the values shown in the following table. Style values not listed in the table will return an error.

Implicit conversions

Implicit conversions do not require specification of either the CAST function or the CONVERT function. Explicit conversions require specification of the CAST function or the CONVERT function. The following illustration shows all explicit and implicit data type conversions allowed for SQL Server system-supplied data types. These include bigint, and sql_variant, and xml. There is no implicit conversion on assignment from the sql_variant data type, but there is implicit conversion to sql_variant.

[!TIP]
The Microsoft Download Center has this chart available for download as a PDF file.

When you convert between datetimeoffset and the character types char, nchar, nvarchar, and varchar, the converted time zone offset part should always have double digits for both HH and MM. For example, -08:00.

[!NOTE]

Because Unicode data always uses an even number of bytes, use caution when you convert binary or varbinary to or from Unicode supported data types. For example, the following conversion does not return a hexadecimal value of 41. It returns a hexadecimal value of 4100: SELECT CAST(CAST(0x41 AS nvarchar) AS varbinary).

Large-value data types

Large-value data types have the same implicit and explicit conversion behavior as their smaller counterparts - specifically, the nvarchar, varbinary, and varchar data types. However, consider the following guidelines: - Conversion from image to varbinary(max), and vice-versa, operates as an implicit conversion, as do conversions between text and varchar(max), and ntext and nvarchar(max).
- Conversion from large-value data types, such as varchar(max), to a smaller counterpart data type, such as varchar, is an implicit conversion, but truncation occurs if the size of the large value exceeds the specified length of the smaller data type.
- Conversion from nvarchar, varbinary, or varchar to their corresponding large-value data types happens implicitly.
- Conversion from the sql_variant data type to the large-value data types is an explicit conversion.
- Large-value data types cannot be converted to the sql_variant data type.

For more information about conversion from the xml data type, see Create Instances of XML Data.

xml data type

When you explicitly or implicitly cast the xml data type to a string or binary data type, the content of the xml data type is serialized based on a defined set of rules. For information about these rules, see Define the Serialization of XML Data. For information about conversion from other data types to the xml data type, see Create Instances of XML Data.

text and image data types

The text and image data types do not support automatic data type conversion. You can explicitly convert text data to character data, and image data to binary or varbinary, but the maximum length is 8000 bytes. If you try an incorrect conversion, for example trying to convert a character expression that includes letters to an int, SQL Server returns an error message.

Output Collation

When the CAST or CONVERT functions output a character string, and they receive a character string input, the output has the same collation and collation label as the input. If the input is not a character string, the output has the default collation of the database, and a collation label of coercible-default. For more information, see Collation Precedence (Transact-SQL).

To assign a different collation to the output, apply the COLLATE clause to the result expression of the CAST or CONVERT function. For example:

SELECT CAST('abc' AS varchar(5)) COLLATE French_CS_AS

Truncating and rounding results

When converting character or binary expressions (binary, char, nchar, nvarchar, varbinary, or varchar) to an expression of a different data type, the conversion operation could truncate the output data, only partially display the output data, or return an error. These cases will occur if the result is too short to display. Conversions to binary, char, nchar, nvarchar, varbinary, or varchar are truncated, except for the conversions shown in the following table.

* = Result length too short to display

E = Error returned because result length is too short to display.

SQL Server guarantees that only roundtrip conversions, in other words conversions that convert a data type from its original data type and back again, yield the same values from version to version. The following example shows such a roundtrip conversion:

DECLARE @myval decimal (5, 2);  
SET @myval = 193.57;  
SELECT CAST(CAST(@myval AS varbinary(20)) AS decimal(10,5));  
-- Or, using CONVERT  
SELECT CONVERT(decimal(10,5), CONVERT(varbinary(20), @myval));  

[!NOTE]
Do not construct binary values, and then convert them to a data type of the numeric data type category. SQL Server does not guarantee that the result of a decimal or numeric data type conversion, to binary, will be the same between versions of SQL Server SQL Server

The following example shows a resulting expression that is too small to display.

USE AdventureWorks2012;  
GO  
SELECT p.FirstName, p.LastName, SUBSTRING(p.Title, 1, 25) AS Title,
    CAST(e.SickLeaveHours AS char(1)) AS [Sick Leave]  
FROM HumanResources.Employee e JOIN Person.Person p 
    ON e.BusinessEntityID = p.BusinessEntityID  
WHERE NOT e.BusinessEntityID >5;  

Here is the result set.

FirstName   LastName      Title   Sick Leave
---------   ------------- ------- --------`
Ken         Sanchez       NULL   *
Terri       Duffy         NULL   *
Roberto     Tamburello    NULL   *
Rob         Walters       NULL   *
Gail        Erickson      Ms.    *
(5 row(s) affected)  

When you convert data types that differ in decimal places, SQL Server will sometimes return a truncated result value, and at other times it will return a rounded value. This table shows the behavior.

For example, the values 10.6496 and -10.6496 may be truncated or rounded during conversion to int or numeric types:

SELECT  CAST(10.6496 AS int) as trunc1,
         CAST(-10.6496 AS int) as trunc2,
         CAST(10.6496 AS numeric) as round1,
         CAST(-10.6496 AS numeric) as round2;

Results of the query are shown in the following table:

When converting data types where the target data type has fewer decimal places than the source data type, the value is rounded. For example, this conversion returns $10.3497:

SELECT CAST(10.3496847 AS money);

SQL Server returns an error message when converting nonnumeric char, nchar, nvarchar, or varchar data to decimal, float, int, numeric. SQL Server SQL Server also returns an error when an empty string (" ") is converted to numeric or decimal.

Certain datetime conversions are nondeterministic

The following table lists the styles for which the string-to-datetime conversion is nondeterministic.

¹ With the exception of styles 20 and 21

Supplementary characters (surrogate pairs)

Starting with SQL Server 2012 (11.x) when using supplementary character (SC) collations, a CAST operation from nchar or nvarchar to an nchar or nvarchar type of smaller length will not truncate inside a surrogate pair. Instead, the operation truncates before the supplementary character. For example, the following code fragment leaves @x holding just 'ab'. There is not enough space to hold the supplementary character.

DECLARE @x NVARCHAR(10) = 'ab' + NCHAR(0x10000);  
SELECT CAST (@x AS NVARCHAR(3));  

When using SC collations, the behavior of CONVERT, is analogous to that of CAST.

Compatibility support

In earlier versions of SQL Server the default style for CAST and CONVERT operations on time and datetime2 data types is 121, except when either type is used in a computed column expression. For computed columns, the default style is 0. This behavior impacts computed columns when they are created, used in queries involving auto-parameterization, or used in constraint definitions.

Under compatibility level 110 and higher, the CAST and CONVERT operations on the time and datetime2 datatypes always have 121 as the default style. If a query relies on the old behavior, use a compatibility level less than 110, or explicitly specify the 0 style in the affected query.

Upgrading the database to compatibility level 110 and higher will not change user data that has been stored to disk. You must manually correct this data as appropriate. For example, if you used SELECT INTO to create a table from a source containing a computed column expression described above, the data (using style 0) would be stored rather than the computed column definition itself. You must manually update this data to match style 121.

Examples

A. Using both CAST and CONVERT

These examples retrieve the name of the product, for those products that have a 3 as the first digit of list price, and converts their ListPrice values to int.

-- Use CAST  
USE AdventureWorks2012;  
GO  
SELECT SUBSTRING(Name, 1, 30) AS ProductName, ListPrice  
FROM Production.Product  
WHERE CAST(ListPrice AS int) LIKE '3%';  
GO  
  
-- Use CONVERT.  
USE AdventureWorks2012;  
GO  
SELECT SUBSTRING(Name, 1, 30) AS ProductName, ListPrice  
FROM Production.Product  
WHERE CONVERT(int, ListPrice) LIKE '3%';  
GO  

B. Using CAST with arithmetic operators

This example calculates a single column computation (Computed) by dividing the total year-to-date sales (SalesYTD) by the commission percentage (CommissionPCT). This value is rounded to the nearest whole number and is then CAST to an int data type.

USE AdventureWorks2012;  
GO  
SELECT CAST(ROUND(SalesYTD/CommissionPCT, 0) AS int) AS Computed  
FROM Sales.SalesPerson   
WHERE CommissionPCT != 0;  
GO  

Here is the result set.

Computed
------
379753754
346698349
257144242
176493899
281101272
0  
301872549
212623750
298948202
250784119
239246890
101664220
124511336
97688107
(14 row(s) affected)  

C. Using CAST to concatenate

This example concatenates noncharacter expressions by using CAST. It uses the AdventureWorksDW database.

SELECT 'The list price is ' + CAST(ListPrice AS varchar(12)) AS ListPrice  
FROM dbo.DimProduct  
WHERE ListPrice BETWEEN 350.00 AND 400.00;  

Here is the result set.

ListPrice
------------------------
The list price is 357.06
The list price is 364.09
The list price is 364.09
The list price is 364.09
The list price is 364.09  

D. Using CAST to produce more readable text

This example uses CAST in the SELECT list, to convert the Name column to a char(10) column. It uses the AdventureWorksDW database.

SELECT DISTINCT CAST(EnglishProductName AS char(10)) AS Name, ListPrice  
FROM dbo.DimProduct  
WHERE EnglishProductName LIKE 'Long-Sleeve Logo Jersey, M';  

Here is the result set.

Name        ListPrice
----------  ---------
Long-Sleev  31.2437
Long-Sleev  32.4935
Long-Sleev  49.99  

E. Using CAST with the LIKE clause

This example converts the money column SalesYTD values to data type int, and then to data typechar(20), so that the LIKE clause can use it.

USE AdventureWorks2012;  
GO  
SELECT p.FirstName, p.LastName, s.SalesYTD, s.BusinessEntityID  
FROM Person.Person AS p   
JOIN Sales.SalesPerson AS s   
    ON p.BusinessEntityID = s.BusinessEntityID  
WHERE CAST(CAST(s.SalesYTD AS int) AS char(20)) LIKE '2%';  
GO  

Here is the result set.

FirstName        LastName            SalesYTD         BusinessEntityID
---------------- ------------------- ---------------- -------------
Tsvi             Reiter              2811012.7151      279
Syed             Abbas               219088.8836       288
Rachel           Valdez              2241204.0424      289
(3 row(s) affected)  

F. Using CONVERT or CAST with typed XML

These examples show use of CONVERT to convert data to typed XML, by using the XML Data Type and Columns (SQL Server).

This example converts a string with white space, text and markup into typed XML, and removes all insignificant white space (boundary white space between nodes):

SELECT CONVERT(XML, '<root><child/></root>')  

This example converts a similar string with white space, text and markup into typed XML and preserves insignificant white space (boundary white space between nodes):

SELECT CONVERT(XML, '<root>          <child/>         </root>', 1)  

This example casts a string with white space, text, and markup into typed XML:

SELECT CAST('<Name><FName>Carol</FName><LName>Elliot</LName></Name>'  AS XML)  

See Create Instances of XML Data for more examples.

G. Using CAST and CONVERT with datetime data

Starting with GETDATE() values, this example displays the current date and time, uses CAST to change the current date and time to a character data type, and then uses CONVERT to display the date and time in the ISO 8601 format.

SELECT   
   GETDATE() AS UnconvertedDateTime,  
   CAST(GETDATE() AS nvarchar(30)) AS UsingCast,  
   CONVERT(nvarchar(30), GETDATE(), 126) AS UsingConvertTo_ISO8601  ;  
GO  

Here is the result set.

UnconvertedDateTime     UsingCast              UsingConvertTo_ISO8601
----------------------- ---------------------- ------------------------------
2006-04-18 09:58:04.570 Apr 18 2006  9:58AM    2006-04-18T09:58:04.570
(1 row(s) affected)  

This example is approximately the opposite of the previous example. This example displays a date and time as character data, uses CAST to change the character data to the datetime data type, and then uses CONVERT to change the character data to the datetime data type.

SELECT   
   '2006-04-25T15:50:59.997' AS UnconvertedText,  
   CAST('2006-04-25T15:50:59.997' AS datetime) AS UsingCast,  
   CONVERT(datetime, '2006-04-25T15:50:59.997', 126) AS UsingConvertFrom_ISO8601 ;  
GO  

Here is the result set.

UnconvertedText         UsingCast               UsingConvertFrom_ISO8601
----------------------- ----------------------- ------------------------
2006-04-25T15:50:59.997 2006-04-25 15:50:59.997 2006-04-25 15:50:59.997
(1 row(s) affected)  

H. Using CONVERT with binary and character data

These examples show the results of binary and character data conversion, using different styles.

--Convert the binary value 0x4E616d65 to a character value.  
SELECT CONVERT(char(8), 0x4E616d65, 0) AS [Style 0, binary to character];  

Here is the result set.

Style 0, binary to character
----------------------------
Name  
(1 row(s) affected)  

This example shows that Style 1 can force result truncation. The characters 0x in the result set force the truncation.

SELECT CONVERT(char(8), 0x4E616d65, 1) AS [Style 1, binary to character];  

Here is the result set.

Style 1, binary to character
------------------------------
0x4E616D
(1 row(s) affected)  

This example shows that Style 2 does not truncate the result, because the result does not include the characters 0x.

SELECT CONVERT(char(8), 0x4E616d65, 2) AS [Style 2, binary to character];  

Here is the result set.

Style 2, binary to character
------------------------------
4E616D65
(1 row(s) affected)  

Convert the character value ‘Name’ to a binary value.

SELECT CONVERT(binary(8), 'Name', 0) AS [Style 0, character to binary];  

Here is the result set.

Style 0, character to binary
----------------------------
0x4E616D6500000000
(1 row(s) affected)  

SELECT CONVERT(binary(4), '0x4E616D65', 1) AS [Style 1, character to binary];  

Here is the result set.

Style 1, character to binary
---------------------------- 
0x4E616D65
(1 row(s) affected)  

SELECT CONVERT(binary(4), '4E616D65', 2) AS [Style 2, character to binary];  

Here is the result set.

Style 2, character to binary  
----------------------------------  
0x4E616D65
(1 row(s) affected)  

I. Converting date and time data types

This example shows the conversion of date, time, and datetime data types.

DECLARE @d1 date, @t1 time, @dt1 datetime;  
SET @d1 = GETDATE();  
SET @t1 = GETDATE();  
SET @dt1 = GETDATE();  
SET @d1 = GETDATE();  
-- When converting date to datetime the minutes portion becomes zero.  
SELECT @d1 AS [date], CAST (@d1 AS datetime) AS [date as datetime];  
-- When converting time to datetime the date portion becomes zero   
-- which converts to January 1, 1900.  
SELECT @t1 AS [time], CAST (@t1 AS datetime) AS [time as datetime];  
-- When converting datetime to date or time non-applicable portion is dropped.  
SELECT @dt1 AS [datetime], CAST (@dt1 AS date) AS [datetime as date], 
   CAST (@dt1 AS time) AS [datetime as time];  

Examples: [!INCLUDEssSDWfull] and [!INCLUDEssPDW]

J. Using CAST and CONVERT

This example retrieves the name of the product for those products that have a 3 in the first digit of their list price, and converts the ListPrice of these products to int. It uses the AdventureWorksDW database.

SELECT EnglishProductName AS ProductName, ListPrice  
FROM dbo.DimProduct  
WHERE CAST(ListPrice AS int) LIKE '3%';  

This example shows the same query, using CONVERT instead of CAST. It uses the AdventureWorksDW database.

SELECT EnglishProductName AS ProductName, ListPrice  
FROM dbo.DimProduct  
WHERE CONVERT(int, ListPrice) LIKE '3%';  

K. Using CAST with arithmetic operators

This example calculates a single column value by dividing the product unit price (UnitPrice) by the discount percentage (UnitPriceDiscountPct). This result is then rounded to the nearest whole number, and finally converted to an int data type. This example uses the AdventureWorksDW database.

SELECT ProductKey, UnitPrice,UnitPriceDiscountPct,  
       CAST(ROUND (UnitPrice*UnitPriceDiscountPct,0) AS int) AS DiscountPrice  
FROM dbo.FactResellerSales  
WHERE SalesOrderNumber = 'SO47355'   
      AND UnitPriceDiscountPct > .02;  

Here is the result set.

ProductKey  UnitPrice  UnitPriceDiscountPct  DiscountPrice
----------  ---------  --------------------  -------------
323         430.6445   0.05                  22
213         18.5043    0.05                  1
456         37.4950    0.10                  4
456         37.4950    0.10                  4
216         18.5043    0.05                  1  

L. Using CAST with the LIKE clause

This example converts the money column ListPrice to an int type, and then to a char(20) type, so that the LIKE clause can use it. This example uses the AdventureWorksDW database.

SELECT EnglishProductName AS Name, ListPrice  
FROM dbo.DimProduct  
WHERE CAST(CAST(ListPrice AS int) AS char(20)) LIKE '2%';  

M. Using CAST and CONVERT with datetime data

This example displays the current date and time, uses CAST to change the current date and time to a character data type, and finally uses CONVERT display the date and time in the ISO 8601 format. This example uses the AdventureWorksDW database.

SELECT TOP(1)  
   SYSDATETIME() AS UnconvertedDateTime,  
   CAST(SYSDATETIME() AS nvarchar(30)) AS UsingCast,  
   CONVERT(nvarchar(30), SYSDATETIME(), 126) AS UsingConvertTo_ISO8601  
FROM dbo.DimCustomer;  

Here is the result set.

UnconvertedDateTime     UsingCast                     UsingConvertTo_ISO8601  
---------------------   ---------------------------   ---------------------------  
07/20/2010 1:44:31 PM   2010-07-20 13:44:31.5879025   2010-07-20T13:44:31.5879025  

This example is the rough opposite of the previous example. This example displays a date and time as character data, uses CAST to change the character data to the datetime data type, and then uses CONVERT to change the character data to the datetime data type. This example uses the AdventureWorksDW database.

SELECT TOP(1)   
   '2010-07-25T13:50:38.544' AS UnconvertedText,  
CAST('2010-07-25T13:50:38.544' AS datetime) AS UsingCast,  
   CONVERT(datetime, '2010-07-25T13:50:38.544', 126) AS UsingConvertFrom_ISO8601  
FROM dbo.DimCustomer;  

Here is the result set.

UnconvertedText         UsingCast               UsingConvertFrom_ISO8601
----------------------- ----------------------- ------------------------
2010-07-25T13:50:38.544 07/25/2010 1:50:38 PM   07/25/2010 1:50:38 PM  

See also

Data Type Conversion (Database Engine)
FORMAT (Transact-SQL)
STR (Transact-SQL)
SELECT (Transact-SQL)
System Functions (Transact-SQL)
Write International Transact-SQL Statements