Datatypes

DB Access Module for Sybase User's Guide

2.3 Datatypes

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

When fetching data or retrieving information about tables, the DB Access Module for Sybase converts the Sybase-specific datatype information provided by the database into RWDBValue::ValueTypes. This mapping is shown in Table 1, which also gives the C++ datatype corresponding to the RWDBValue::ValueType.
When creating tables, the DB Access Module for Sybase maps the given RWDBValue::ValueType into a Sybase-specific 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 SourcePro C++ API Reference Guide.

Table 1: Datatype mapping when retrieving data

Adaptive Server Datatypes	RWDBValue::ValueType	C++ Datatype
`char(n)` `varchar(n)` `text`	`String`	*RWCString*
`nchar(n)` `nvarchar(n)`	`MBString`¹	*RWDBMBString*1
`unichar(n)`, `univarchar(n)` `unitext`	`UString`	*RWBasicUString* or *RWUString* *RWUString*
`binary(n)` `varbinary(n)` `image` `timestamp`	`Blob`	*RWDBBlob*
`bit` `tinyint` `smallint`	`Short`	`short int`
`int`	`Long`	`long int`
`decimal(p,0) p <= 9` `numeric(p,0) p <= 9`	`Long`	`long int`
`decimal(p,0) 10 <= p < 19` `numeric(p,0) 10 <= p < 19`	`LongLong`	`long long`
`decimal(p,0) p >= 19` `numeric(p,0) p >= 19`	`Decimal`	*RWDecimalPortable*
`decimal(p,s)` `numeric(p,s)`	`Decimal`	*RWDecimalPortable*
`float(p)` `double precision`	`Double`	`double`
`real`	`Float`	`float`
`money` `smallmoney`	`Decimal`	*RWDecimalPortable*
`datetime` `smalldatetime`²	`DateTime`	*RWDBDateTime³ RWDateTime*

The Sybase Adaptive Server usertype value, when available, is used to differentiate standard and national character strings. See Section 2.11 on internationalization.
Values of type datetime and smalldatetime are affected by the time zone setting on either RWDBDatabase or RWDBConnection while sending and retrieving data. The time zone setting can be set programmatically with the timeZone() method in each of these classes.
RWDBDateTime is now deprecated. Please use RWDateTime.

Table 2: Datatype mapping when creating tables

RWDBValue::ValueType	Adaptive Server Datatype
`Char` `UnsignedChar` `Tiny` `UnsignedTiny`	`tinyint`
`String`	if 0 < `length` <= 255, `varchar` using the `storageLength` of the *RWDBColumn*, otherwise `text`
`WString` `MBString`	if 0 < `length` <= 255, `nvarchar` using the `storageLength` of the *RWDBColumn*, otherwise `text`
`UString`	`univarchar`, using the `storageLength` of the *RWDBColumn*
`Blob`	if 0 < `length` <= 255, `varbinary` using the `storageLength` of the *RWDBColumn*, otherwise `image`
`Short` `UnsignedShort`	`smallint`
`Int` `UnsignedInt`	`int`
`Long` `UnsignedLong`	`int`
`Float`	`real`
`Double`	`float(p)`, using precision of column
`Decimal`	`money` or `decimal(p,s)` using precision and scale of column. See below.
`Date` `DateTime`	`datetime`
`Duration`	Not supported by the Sybase client

2.3.1 Restrictions on the Use of Datatypes

Sybase Open Client Client-Library and Sybase Adaptive Server Enterprise place restrictions on the use of certain datatypes. Where possible, the DB Interface Module is flexible about datatypes. However, there are some situations where conversions are not possible, and in these cases your application must be aware of the contexts in which certain datatypes can be used. Table 3 outlines the restrictions associated with each DB Interface Module type.

Table 3: Restrictions on the use of DB Interface Module datatypes

RWDBValue::ValueType	Restrictions
`Char` `UnsignedChar`	No restrictions.
`String` `WString` `MBString` `UString`	Not supported on *RWDBBoundExpr* if string size is bigger than 16384 bytes.
`Blob`	Not supported on RWDBBoundExpr.
`Short` `UnsignedShort`	No restrictions.
`Int` `UnsignedInt`	No restrictions.
`Long` `UnsignedLong`	No restrictions.
`Double`	No restrictions.
`Float`	No restrictions.
`Decimal`	The precision and scale of a value can vary depending on the version of the Sybase client and server. Consistent versions of clients and servers can eliminate difficulties in conversions.
`Date`	No restrictions.
`DateTime`	Accuracy limited to 3.33 milliseconds by Sybase.
`Duration`	Not supported by the Sybase client
`LongLong` `UnsignedLongLong`	Table creation not supported.
`LongDouble`	No restrictions.

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