Data Types

DB Access Module for MySQL 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 MySQL converts the MySQL type value 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 MySQL maps the given RWDBValue::ValueType into a MySQL type code. This mapping is shown in Table 2.

The RWDBValue::ValueType, 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

MySQL Data Type	RWDBValue::ValueType	C++ Data Type
`decimal numeric`	`Decimal`	*RWDecimalPortable*
`bigint`	`UnsignedLongLong, LongLong`	`unsigned long long, long long`
`tinyblob, blob, mediumblob, longblob`	`Blob`	*RWDBBlob*
`double`	`Double`	`double`
`float`	`Float`	`float`
`tinyint`	`Char, UnsignedChar`	`char, unsigned char`
`smallint`	`Short, UnsignedShort`	`short, unsigned short`
`integer, mediumint`	`Long, UnsignedLong`	`long, unsigned long`
`char, varchar, tinytext, mediumtext, text, longtext, enum, set`	`String`	*RWCString*
`date`	`Date`	*RWDate*
`datetime, time, timestamp`	`DateTime`	*RWDBDateTime¹, RWDateTime*
`year`	`UnsignedShort`	`unsigned short`

RWDBDateTime is deprecated. Please use RWDateTime.

Table 2: Type mapping when creating tables

RWDBValue::ValueType	MySQL Data Types
`Blob`	`MEDIUMBLOB` if length is `RWDB_NO_TRAIT`. If 0<= length <= 255 `TINYBLOB`. If 256 <= length <=65,535 `BLOB`. If 65,536 <= length <= 16,777,215 `MEDIUMBLOB.` Otherwise, `LONGBLOB`.
`Tiny, UnsignedTiny, Char, UnsignedChar`	`TINYINT`
`Date`	`DATE`
`DateTime`	`DATETIME`
`Decimal (p,s)`	`DECIMAL` using precision and scale of column. If p <= 0 defaults to 8. If s <= 0 defaults to 0.
`Double`	`DOUBLE`
`Float (P)`	`FLOAT` if precision is `RWDB_NO_TRAIT`. Otherwise, `FLOAT (p)` using precision of column.
`Int`, `UnsignedInt, Long`, `UnsignedLong`	`INT`
`Short`, `UnsignedShort`	`SMALLINT`
`LongLong, UnsignedLongLong`	`BIGINT`
`String`	`MEDIUMTEXT` if length is `RWDB_NO_TRAIT`. If 0<= length <= 255 `VARCHAR(length)` using the `storageLength` of the *RWDBColumn*. If 256 <= length <= 65,535 `TEXT`. If 65,536 <= length <= 16,777,215 `MEDIUMTEXT.` Otherwise `LONGTEXT.`

2.3.1 Restrictions on the Use of Data Types

Table 3 outlines the known restrictions associated with each DB Interface Module value type.

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

RWDBValue::ValueType	Restrictions
`Blob`	No restrictions.
`Char, UnsignedChar`	No restrictions.
`Blob`	No restrictions
`Char, UnsignedChar`	No restrictions
`Date`	No restrictions.
`DateTime`	No restrictions.
`Decimal`	No restrictions.
`Double`	No restrictions.
`Duration`	This data type is not supported.
`Float`	No restrictions.
`Int, UnsignedInt`	No restrictions.
`Long, UnsignedLong`	No restrictions.
`LongLong, UnsignedLongLong`	No restrictions.
`MBString`	This data type is not supported.
`LongDouble`	No restrictions.
`String`	No restrictions.
`Short, UnsignedShort`	No restrictions.
`WString`	This data type is not supported.
`UString`	This data type is not supported.

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