Data Types

DB Access Module for PostgreSQL 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 PostgreSQL converts the PostgreSQL specific datatype information provided by the database 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 PostgreSQL maps the given RWDBValue::ValueType into a PostgreSQL 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 DB Interface Module Reference Guide.

Table 1: Type mapping when retrieving data

PostgreSQL Data Type	RWDBValue:: ValueType	C++ Data Type
`bigint`	`LongLong`	`long long`
`bigserial`	`LongLong`	`long long`
`bit, bit varying(n)`	String	*RWCString*
`boolean`	String	*RWCString*
`box`	`String`	*RWCString*
`bytea`	`Blob`	*RWDBBlob*
`char(n)`	`String`	*RWCString*
`varchar(n)`	`String`	*RWCString*
`cidr`	`String`	*RWCString*
`circle`	`String`	*RWCString*
`date`	`Date`	*RWDate*
`double precision`	`Double`	`double`
`inet`	`String`	*RWCString*
`integer`	`Long`	`long int`
`interval(p)`	`Duration`	*RWDBDuration*
`line`	`String`	*RWCString*
`lseg`	`String`	*RWCString*
`macaddr`	`String`	*RWCString*
`money`	`String`	*RWCString*
`numeric`	`Decimal`	*RWDecimalPortable*
`path`	`String`	*RWCString*
`point`	`String`	*RWCString*
`polygon`	`String`	*RWCString*
`real`	`Float`	`float`
`smallint`	`Short`	`short int`
`serial`	`Long`	`long int`
`text`	`String`	*RWCString*
`time(p)`	`DateTime`	*RWDateTime*
`time(p) with time zone`	`DateTime`	*RWDateTime*
`timestamp(p)`	`DateTime`	*RWDateTime*
`timestamp(p) with time zone`	`DateTime`	*RWDateTime*

Table 2: Type mapping when creating tables

RWDBValue::ValueType	PostgreSQL Data Type
`Blob`	`bytea`
`Char, UnsignedChar,` `Tiny, UnsignedTiny,` `Short, UnsignedShort`	`smallint`
`Date`	`date`
`DateTime`	`timestamp[(p)]` using `precision` of column if specified
`Decimal`	`numeric(p,s)` using `precision` and `scale` of column if specified
`Duration`	`interval[(p)]` using `precision` of column if specified
`Double`	`double precision`
`Float`	`real`
`Int, UnsignedInt`	`integer`
`Long, UnsignedLong`	`integer`
`LongLong, UnsignedLongLong`	`bigint`
`String`	`varchar(n)` if `storageLength` is specified, else `text`

2.3.1 Restrictions on the Use of Data Types

The PostgreSQL database places 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. In these cases your applications must be aware of the contexts in which certain datatypes can be used. 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`	Only the PostgreSQL `DateStyle` `ISO, MDY` is supported.
`DateTime`	Accuracy provided by PostgreSQL is microseconds, but *RWDateTime* is limited to milliseconds. Only the PostgreSQL `DateStyle ISO 8601` format in `MDY` mode is supported.
`Decimal`	No restrictions.
`Double`	No restrictions.
`Duration`	No restrictions.
`Float`	No restrictions.
`Int, UnsignedInt`	No restrictions.
`Long, UnsignedLong`	No restrictions.
`MBString`	This data type is not supported.
`LongLong, UnsignedLongLong`	No restrictions.
`LongDouble`	No restrictions.
`String`	No restrictions.
`Short, UnsignedShort`	No restrictions.
`WString`	This data type is not supported.
`UString`	This data type is not supported.

2.3.2 Serial Columns in Tables

If a table contains a SERIAL column, PostgreSQL gives you two options:

You may explicitly specify a value for the column.
You may automatically assign a value to the column when a row is inserted.

Therefore, to let PostgreSQL assign the value, you must skip that column when using an RWDBInserter. Please see the method RWDBInserter::operator[] in the DB Interface Module Class Reference.

When reading a table that contains one or more serial columns, serial columns are treated as regular columns.

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