SQL Types

One of the key principles of a relational database system is the management of strongly-typed values, according to a set of types native to the system or defined by the users.

All the types of the system, including the primitives, are nullable and support comparison and assignment to NULL.

Primitive Types

The primitive types are elementary forms of data types that can be used by more structured types (eg. User-Defined Types).

Numeric Types

Conceptually the system handles numerics with a single structure of data that is scalable and dynamic (SqlNumber), manipulated by specific type configurations.

The following SQL integer types are supported:

• TINYINT
• SMALLINT
• INT, INTEGER
• BIGINT

The floating point number types allow the specification of the size of the number and the precision of the numeric:

• FLOAT, REAL
• DOUBLE
• NUMERIC, DECIMAL

Boolean Type

These kind of data values can handle just one single bit to indicate a boolean state (either true or false). It is possible to specify a boolean type using the BOOLEAN or BIT.

String Types

Strings handle sequence of characters in a given format and encoding, to represent data in a human-readable form.

The system supports two kind of string:

• Simple Strings (handled by SqlString object): these are strings supporting a maximum number of 64.000 characters
• Long Strings (handled by SqlLongString object): they are stored as a Large Object, given a maximum size specified

The default encoding of the system is UTF-16, where not specified explicitly, that represents characters in a 2-byte form, using a wider set of the Unicode maps.

The simple strings supported are the following:

• CHAR: represents a string with a fixed size specified
• VARCHAR, STRING: supports a variable size string given a maximum number of characters specified

To define a long string is is possible to use the following types:

• CLOB, LONG CHARACTER VARYING, LONG VARCHAR

Binary Types

Date Types

Interval Types

User-Defined Types (UDT)

Module-Provided Types (MPT)

When a developer provides a module to the system, it is possible to define one or more data-types to be handled.

For the system to recognize and handle a module-specified type, the developer must do the following:

• Provide one or more objects that implement ISqlObject contract
• Inherit from SqlType object and override the specific features for the type, handling the implemented ISqlObject
• Implement a ITypeResolver instance that will analyze a passed name and metadata to construct the type
• Bind the implementation of the ITypeResolver into the System Scope at the build of the system

When defining a module, it is also possible to provide functions to operate on the type provided.

Xml Type

Spatial Types