Data Types

DB Access Module for ODBC User's Guide
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2.3 Data Types

The classes RWDBColumn and RWDBValue have an associated RWDBValue::ValueType that specifies the data type of the database column or field being referenced. Mapping between this data type and the database vendor type runs in both directions:

When fetching data or retrieving information about tables, the DB Access Module for ODBC converts the SQL data type provided by ODBC into RWDBValue::ValueTypes. This mapping is shown in Table 1, which also gives the C++ data type corresponding to the RWDBValue::ValueType.
When creating tables, the DB Access Module for ODBC maps the given RWDBValue::ValueType into an SQL data type. This mapping is shown in Table 2.

The RWDBValue::ValueTypes, accessible through the type() method, are uniform across all Access Modules. For a complete explanation of the DB Interface Module data model, see Chapter 7, "The Data Model," in the DB Interface Module User's Guide, and RWDBValue in the DB Interface Module Reference Guide.

Table 1: Type mapping when retrieving data

ODBC Data Type	RWDBValue::ValueType	C++ Data Type
`SQL_NUMERIC SQL_DECIMAL`	`Decimal`	*RWDecimalPortable*
`SQL_BINARY SQL_VARBINARY SQL_LONGVARBINARY`	`Blob`	*RWDBBlob*
`SQL_BIT`	`UnsignedChar`	`unsigned char`
`SQL_DOUBLE SQL_FLOAT`	`Double`	`double`
`SQL_INTEGER`	`Long/UnsignedLong`	`long int/unsigned long int`
`SQL_INTERVAL`	`Duration`	*RWDBDuration*
`SQL_LONGVARCHAR SQL_VARCHAR SQL_CHAR`	`String`	*RWCString*
`SQL_REAL`	`Float`	`float`
`SQL_SMALLINT`	`Short/UnsignedShort`	`short int/unsigned short int`
`SQL_TYPE_DATE`	`Date`	*RWDate*
`SQL_TYPE_TIME` `SQL_TYPE_TIMESTAMP`	`DateTime`	*RWDBDateTime¹ RWDateTime*
`SQL_WLONGVARCHAR SQL_WVARCHAR SQL_WCHAR`	`WString`	*RWWString*
`SQL_BIGINT`	`LongLong/UnsignedLongLong`	`long long/unsigned long long`

RWDBDateTime is deprecated. Please use RWDateTime.

Table 2: Type mapping when creating tables

RWDBValue::ValueType	**Possible ODBC Data Types: the type chosen is the first type supported by the underlying driver**
`Blob`	If 0 < `length` <= 255, `{SQL_VARBINARY, SQL_BINARY, SQL_LONGVARBINARY, SQL_LONGVARCHAR}` using the `storageLength` of the *RWDBColumn* if applicable; otherwise, `{SQL_LONGVARBINARY,SQL_VARBINARY,` `SQL_BINARY, SQL_LONGVARCHAR}` using the `storageLength` of the *RWDBColumn* if applicable
`Char`, `UnsignedChar`	`{SQL_TINYINT, SQL_SMALLINT, SQL_INTEGER, SQL_DECIMAL, SQL_NUMERIC}`
`Date`	`{SQL_TYPE_DATE, SQL_TYPE_TIMESTAMP}`
`DateTime`	`{SQL_TYPE_TIMESTAMP, SQL_TYPE_DATE}`
`Decimal`	`{SQL_DECIMAL, SQL_NUMERIC, SQL_DOUBLE},` using the precision and scale of the *RWDBColumn* if applicable
`Double`	`{SQL_DOUBLE, SQL_FLOAT, SQL_DECIMAL, SQL_NUMERIC }`
`Duration`	`{SQL_INTERVAL_SECOND}`
`Float`	`{SQL_REAL, SQL_DOUBLE, SQL_FLOAT, SQL_DECIMAL, SQL_NUMERIC}` using the precision and scale of the *RWDBColumn* if applicable
`Int`, `UnsignedInt`	`{SQL_SMALLINT, SQL_INTEGER, SQL_REAL, SQL_DOUBLE, SQL_FLOAT, SQL_DECIMAL, SQL_NUMERIC}`
`Long`, `UnsignedLong`	`{SQL_INTEGER, SQL_REAL, SQL_DOUBLE, SQL_FLOAT, SQL_DECIMAL, SQL_NUMERIC}`
`LongLong, UnsignedLongLong`	`{SQL_BIGINT, SQL_DECIMAL`¹`, SQL_REAL}`
`Short`, `UnsignedShort`	`{SQL_SMALLINT, SQL_INTEGER, SQL_REAL, SQL_DOUBLE, SQL_FLOAT, SQL_DECIMAL, SQL_NUMERIC}`
`String`	If 0 < `length` <= 255, `{SQL_VARCHAR, SQL_CHAR, SQL_LONGVARCHAR}`; otherwise, `{SQL_LONGVARCHAR, SQL_VARCHAR, SQL_CHAR}` using the storageLength of the *RWDBColumn*, if applicable.
`WString`	If 0 < `length` <= 254, `{SQL_WVARCHAR, SQL_WCHAR, SQL_WLONGVARCHAR}` using the `storageLength` of the *RWDBColumn* if applicable; otherwise, `{SQL_WLONGVARCHAR,` `SQL_WVARCHAR, SQL_WCHAR}` using the `storageLength` of the *RWDBColumn* if applicable.

The precision of the decimal type created is 20.

2.3.1 Restrictions on the Use of Data Types

Neither the DB Interface Module nor the ODBC specification impose restrictions on the use of most data types, but individual ODBC drivers may. Check for specific restrictions in the documentation provided with your ODBC driver. Table 3 outlines the known restrictions associated with each DB Interface Module type.

Table 3: Restrictions on the use of DB Interface Module data types

RWDBValue::ValueType	Restrictions
`Blob`	No restrictions.
`Char, UnsignedChar`	No restrictions.
`Date`	No restrictions.
`DateTime`	No restrictions.
`Decimal`	No restrictions.
`Double`	No restrictions.
`Duration`	No restrictions.
`Float`	No restrictions.
`Int, UnsignedInt`	No restrictions.
`Long, UnsignedLong`	No restrictions.
`LongLong, UnsignedLongLong`	No restrictions.
`MBString`	This data type is not supported.
`String`	No restrictions.
`Short, UnsignedShort`	No restrictions.
`WString`	This data type may not be supported -- check your driver documentation.
`UString`	This data type is not supported.
`LongDouble`	For input binding, long double value inserted should be in range of what database supports. Please check your database documentation for details.

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