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Data types overview

In 4D, data are handled according to their type in two places: database fields and the 4D language.

Although they are usually equivalent, some data types available at the database level are not directly available in the language and are automatically converted. Conversely, some data types can only be handled through the language. The following table lists all available data types and how they are supported/declared:

Data Types	Database support(1)	Language support	var declaration	C_ or ARRAY declaration
Alphanumeric	Sim	Converted to text	-	-
Texto	Sim	Sim	Texto	C_TEXT, ARRAY TEXTO
Date	Sim	Sim	Date	C_DATE, ARRAY DATE
Hora	Sim	Sim	Hora	C_TIME, ARRAY TIME
Booleano	Sim	Sim	Booleano	C_BOOLEAN, ARRAY BOOLEAN
Integer	Sim	Converted to longint	Integer	ARRAY INTEGER
Longint	Sim	Sim	Integer	C_LONGINT, ARRAY LONGINT
Longint 64 bits	Yes (SQL)	Converted to real	-	-
Real	Sim	Sim	Real	C_REAL, ARRAY REAL
Undefined	-	Sim	-	-
Null	-	Sim	-	-
Ponteiro	-	Sim	Ponteiro	C_POINTER, ARRAY POINTER
Imagem	Sim	Sim	Imagem	C_PICTURE, ARRAY PICTURE
BLOB	Sim	Sim	Blob	C_BLOB, ARRAY BLOB
Objeto	Sim	Sim	Objeto	C_OBJECT, ARRAY OBJECT
Collection	-	Sim	Collection	C_COLLECTION
Variant(2)	-	Sim	Variant	C_VARIANT

(1) Note that ORDA handles database fields through objects (entities) and thus, only supports data types available to these objects. For more information, see the Object data type description.

(2) Variant is actually not a data type but a variable type that can contain a value of any other data type.

Default values

When variables are typed by means of a compiler directive, they receive a default value, which they will keep during the session as long as they have not been assigned.

The default value depends on the variable type:

Type	Default value
Booleen	False
Date	00-00-00
Longint	0
Hora	00:00:00
Imagem	picture size=0
Real	0
Ponteiro	Nil=true
Texto	""
Blob	Blob size=0
Objeto	null
Collection	null
Variant	undefined

Converting data types

The 4D language contains operators and commands to convert between data types, where such conversions are meaningful. The 4D language enforces data type checking. For example, you cannot write: "abc"+0.5+!12/25/96!-?00:30:45?. This will generate syntax errors.

The following table lists the basic data types, the data types to which they can be converted, and the commands used to do so:

Data Type to Convert	to String	to Number	to Date	to Time	to Boolean
String (1)		Num	Date	Hora	Bool
Number (2)	String				Bool
Date	String				Bool
Hora	String				Bool
Booleano		Num

(1) Strings formatted in JSON can be converted into scalar data, objects, or collections, using the JSON Parse command.

(2) Time values can be treated as numbers.

Note: In addition to the data conversions listed in this table, more sophisticated data conversions can be obtained by combining operators and other commands.