2.3 Datatypes

Data fetched from a database into a DBTools.h++ application are stored internally by DBTools.h++ in instances of the RWDBValue class. Most applications can ignore RWDBValue and fetch data directly into C++ variables. If you do need to use it, Table 1 shows how Oracle8 datatypes are mapped into RWDBValues, and lists the C++ class or datatype appropriate for each Oracle8 datatype. See the Oracle8 Application Developer's Guide for more information on Oracle8 datatypes.

Table 1 -- Type mapping when retrieving data

Oracle8 Datatype	RWDBValue::ValueType	C++ Datatype
`CHAR(n) VARCHAR2(n)`	`String`	*RWCString*
`NCHAR(n)` `NVARCHAR2(n)`	`String`¹	*RWCString*²
`LONG`	`String`	*RWCString*
`CLOB`	`String`	*RWCString*
`RAW(n), LONG RAW`	`Blob`	*RWDBBlob*
`BLOB`	`Blob`	*RWDBBlob*
`NUMBER(p,0) p<10`	`Long`	`long int`
`NUMBER(p,0) p>=10`	`Decimal`	*RWDecimalPortable*
`NUMBER(p,s) p>=10`	`Decimal`	*RWDecimalPortable*
`NUMBER(p,s) p<10`	Double	`double`
`FLOAT(p)`	`Double`	`double`
`DATE`	`DateTime`	*RWDBDateTime*
`ROWID`	`String`	*RWCString*
`MLSLABEL`	`String`	*RWCString*

1	Oracle8 doesn't differentiate when returning standard and national character strings. See Section 2.9.1 on return types.
2	See the previous footnote.

When an application uses DBTools.h++ to create an Oracle8 table, RWDBValue::ValueType is used to define the table's schema. Table 2 shows how DBTools.h++ maps its datatypes to Oracle8 datatypes when defining a schema.

Table 2 -- Type mapping when creating tables

RWDBValue::ValueType	Oracle8 Datatype
`Blob`	`RAW(n)`, if `length` is less than or equal to 2000; otherwise, `LONG` `RAW` or `BLOB` based on `nativeType()`. See also the *RWDBOracle8EnvironmentHandle* method `ociLocatorForDefaultBlob()`.
`Char`, `UnsignedChar`	`NUMBER(d)`, where `d` is the number of digits needed to store the maximum value a `char` can express on the client machine
`Date`	`DATE`
`DateTime`	`DATE`
`Decimal`	`NUMBER(p,s)` using `precision` and `scale` of column
`Double`	`FLOAT(126)`
`Duration`	Not supported by Oracle8
`Float`	`FLOAT(p)` using `precision` of column
`Int`, `UnsignedInt`	`NUMBER(d)`, where `d` is the number of digits needed to store the maximum value an `int` can express on the client machine
`Long`, `UnsignedLong`	`NUMBER(d)`, where `d` is the number of digits needed to store the maximum value a `long` can express on the client machine
`MBString`, `WString`	`NVARCHAR2`
`Short`, `UnsignedShort`	`NUMBER(d)`, where `d` is the number of digits needed to store the maximum value a short can express on the client machine
`String`	`VARCHAR`, if `length` is less than or equal to 4000; otherwise, `LONG` or `CLOB` based on `nativeType()`. See also the *RWDBOracle8EnvironmentHandle* method `ociLocatorForDefaultString()`.

2.3.1 Restrictions on the Use of Datatypes

Oracle8 OCI and servers place restrictions on the use of certain datatypes. Where possible, DBTools.h++ tries to be flexible about datatypes. However, there are 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 DBTools.h++ type.

Table 3 -- Restrictions on the use of DBTools.h++ datatypes

RWDBValue::ValueType	Restrictions
`Blob`	No restrictions
`Char`, `UnsignedChar`	No restrictions
`Date`	No restrictions
`DateTime`	No restrictions
`Decimal`	No restrictions
`Double`	No restrictions
`Duration`	Not supported by Oracle8
`Float`	No restrictions
`Int`, `UnsignedInt`	No restrictions
`Long`, `UnsignedLong`	No restrictions
`MBString`, `WString`	Limited to 4,000 bytes
`Short`, `UnsignedShort`	No restrictions
`String`	No restrictions