Because int has a higher precedence than varchar, SQL Server attempts to convert the string to an integer and fails because this string cannot be converted to an integer. In order to evaluate the expression + ' is not a string.', SQL Server follows the rules of data type precedence to complete the implicit conversion before the result of the expression can be calculated. Msg 245, Level 16, State 1, Line 3 Conversion failed when converting the varchar value ' is not a string.' to data type int. In this case, the SELECT statement throws the following error: The following example, shows a similar script with an int variable instead: DECLARE INT The int value of 1 is converted to a varchar, so the SELECT statement returns the value 1 is a string. For comparison operators or other expressions, the resulting data type depends on the rules of data type precedence.Īs an example, the following script defines a variable of type varchar, assigns an int type value to the variable, then selects a concatenation of the variable with a string. For implicit conversions, assignment statements such as setting the value of a variable or inserting a value into a column result in the data type that was defined by the variable declaration or column definition. When SQL Server performs an explicit conversion, the statement itself determines the resulting data type. While the above chart illustrates all the explicit and implicit conversions that are allowed in SQL Server, it does not indicate the resulting data type of the conversion. There is no implicit conversion on assignment from the sql_variant data type, but there is implicit conversion to sql_variant. These include xml, bigint, and sql_variant. The following illustration shows all explicit and implicit data type conversions that are allowed for SQL Server system-supplied data types. Use CONVERT instead of CAST to take advantage of the style functionality in CONVERT.
#Sql server convert string to double code#
Use CAST instead of CONVERT if you want Transact-SQL program code to comply with ISO. For example, the following CAST function converts the numeric value of $157.27 into a character string of '157.27': CAST ( $157.27 AS VARCHAR(10) )
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The CAST and CONVERT functions convert a value (a local variable, a column, or another expression) from one data type to another. SYSDATETIME() implicitly converts to date style 21.Įxplicit conversions use the CAST or CONVERT functions. GETDATE() implicitly converts to date style 0. For example, when a smallint is compared to an int, the smallint is implicitly converted to int before the comparison proceeds. SQL Server automatically converts the data from one data type to another. Implicit conversions are not visible to the user. Implicit and explicit conversionĭata types can be converted either implicitly or explicitly. When you convert between an application variable and a SQL Server result set column, return code, parameter, or parameter marker, the supported data type conversions are defined by the database API. When data from a Transact-SQL result column, return code, or output parameter is moved into a program variable, the data must be converted from the SQL Server system data type to the data type of the variable.When data from one object is moved to, compared with, or combined with data from another object, the data may have to be converted from the data type of one object to the data type of the other.Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL Endpoint in Microsoft Fabric Warehouse in Microsoft Fabricĭata types can be converted in the following scenarios:
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