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Data Type Usage

The SQL Server Native Client ODBC driver and SQL Server impose the following use of data types.

Data type

Limitation

Date literals

Date literals, when stored in a SQL_TYPE_TIMESTAMP column (SQL Server data types of datetime or smalldatetime), have a time value of 12:00:00.000 A.M.

money and smallmoney

Only the integer parts of the money and smallmoney data types are significant. If the decimal part of SQL money data is truncated during data type conversion, the SQL Server Native Client ODBC driver returns a warning, not an error.

SQL_BINARY (nullable)

When connected to an instance of SQL Server version 6.0 and earlier, if a SQL_BINARY column is nullable, the data that is stored in the data source is not padded with zeroes. When data from such a column is retrieved, the SQL Server Native Client ODBC driver pads it with zeroes on the right. However, data that is created in operations performed by SQL Server, such as concatenation, does not have such padding.

Also, when data is placed in such a column in an instance of SQL Server 6.0 or earlier, SQL Server truncates the data on the right if it is too long to fit into the column.

NoteNote
The SQL Server Native Client ODBC driver does support connecting to SQL Server 6.5 and earlier.

SQL_CHAR (truncation)

When connected to an instance of SQL Server 6.0 and earlier, and data is placed into a SQL_CHAR column, SQL Server truncates it on the right without warning if the data is too long to fit into the column.

NoteNote
The SQL Server Native Client ODBC driver does support connecting to SQL Server 6.5 and earlier.

SQL_CHAR (nullable)

When connected to an instance of SQL Server 6.0 and earlier, if a SQL_CHAR column is nullable, the data that is stored in the data source is not padded with blanks. When data from such a column is retrieved, the SQL Server Native Client ODBC driver pads it with blanks on the right. However, data that is created in operations performed by SQL Server, such as concatenation, does not have such padding.

NoteNote
The SQL Server Native Client ODBC driver does support connecting to SQL Server 6.5 and earlier.

SQL_LONGVARBINARY, SQL_LONGVARCHAR, SQL_WLONGVARCHAR

Updates of columns with SQL_LONGVARBINARY, SQL_LONGVARCHAR, or SQL_WLONGVARCHAR data types (using a WHERE clause) that affect multiple rows are fully supported when connected to an instance of SQL Server 6.x and later. When connected to an instance of SQL Server 4.2x, an S1000 error, "Partial insert/update. The insert/update of a text or image column(s) did not succeed" is returned if the update affects more than one row.

NoteNote
The SQL Server Native Client ODBC driver does support connecting to SQL Server 6.5 and earlier.

String function parameters

string_exp parameters to the string functions must be of data type SQL_CHAR or SQL_VARCHAR. SQL_LONG_VARCHAR data types are not supported in the string functions. The count parameter must be less than or equal to 8,000 because the SQL_CHAR and SQL_VARCHAR data types are limited to a maximum length of 8,000 characters.

Time literals

Time literals, when stored in a SQL_TIMESTAMP column (SQL Server data types of datetime or smalldatetime), have a date value of January 1, 1900.

timestamp

Only a NULL value can be manually inserted into a timestamp column. However, because timestampcolumns are automatically updated by SQL Server, a NULL value is overwritten.

tinyint

The SQL Server tinyint data type is unsigned. A tinyint column is bound to a variable of data type SQL_C_UTINYINT by default.

Alias data types

When connected to an instance of SQL Server 4.2x, the ODBC driver adds NULL to a column definition that does not explicitly declare a column's nullability. Therefore, the nullability that is stored in the definition of an alias data type is ignored.

When connected to an instance of SQL Server 4.2x, columns with an alias data type that has a base data type of char or binary and for which no nullability is declared are created as data type varchar or varbinary. SQLColAttribute, SQLColumns, and SQLDescribeCol return SQL_VARCHAR or SQL_VARBINARY as the data type for these columns. Data that is retrieved from these columns is not padded.

NoteNote
The SQL Server Native Client ODBC driver does support connecting to SQL Server 6.5 and earlier.

LONG data types

data-at-execution parameters are restricted for both the SQL_LONGVARBINARY and the SQL_LONGVARCHAR data types.

Large value types

The SQL Server Native Client ODBC driver will expose varchar(max), varbinary(max), and nvarchar(max) types as SQL_VARCHAR, SQL_VARBINARY and SQL_WVARCHAR (respectively) in APIs that accept or return ODBC SQL data types.

User-defined type (UDT)

UDT columns are mapped as SQL_SS_UDT. If a UDT column is mapped explicitly to another type in the SQL statement using the ToString() or ToXMLString() methods of the UDT, or via the CAST/CONVERT functions, the type of the column in the result set will reflect the actual type to which the column was converted.

The SQL Server Native Client ODBC driver can only bind to a UDT column as binary. SQL Server only supports conversion between the SQL_SS_UDT and SQL_C_BINARY data types.

XML

SQL Server will automatically convert XML to Unicode text. The XML type is mapped as SQL_SS_XML.

See Also

Concepts

Processing Results (ODBC)