Field Type Use Recommendations

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Field Type Use Recommendations

If you want to define a new field into the LANSA dictionary use this decision tree:

Is the field a Date or a Time?

To store a unique day use type Date.

To store a unique moment in time use type DateTime (in preference to two separate Date and Time fields).

To store a non-unique time, which is unusual, use Time.

Is it a True/False value? If so, use Boolean.

Is it a number? If there are no decimal places use type Integer otherwise use type Packed.

Then it must be a string of characters or some other stream of bytes.

Is it normally kept in a specialized type of file or document (eg: an image, a sound, an MS-Word document or an XML document)? Use type BLOB.

Do you expect it to be subjected to normal code page conversions? If not, use VarBinary unless your data is always the same length, in which case you may choose to use Binary.

Will the field be 256 bytes or less and be best stored as a fixed length field? If yes, and it only needs to support one language at execution time, use type Alpha.

Will it ever be longer than 65535 bytes? Use type CLOB.

Do you store the field as variable length with any trailing blanks significant (for example, included in field concatenation operations)? If it only needs to support one language at execution time, use type String. Otherwise, use type NVarChar.

Otherwise it is fixed length. If it only needs to support one language at execution time, use type Char. Otherwise, use type NChar.

All other types are provided for compatibility with non-LANSA database tables. Generally you should avoid using them when defining new fields or columns in new DBMS tables.

Commonly Used Field Types

Type	Description	Typical DBMS Storage Type	Maximum Dictionary Definable Length	Subject to Code Page Conversions	Notes	Useable in RDML or RDMLX Programs
Integer	Integer	INTEGER	4 bytes.		Hardware and compiler behaviors may vary.	RDMLX
Packed	Standard decimal number	DECIMAL	RDMLX programs: 63 digits of which up to 63 may be decimals RDML programs: 30 digits of which up to 9 may be decimals	N/A		Both
String	Variable length alphanumeric string with a dictionary defined maximum length.	VARCHAR (variable length)	65535	YES	Not padded with blanks to the dictionary defined maximum length, except that a zero length string has 1 space added.	RDMLX
VarBinary	Exactly the same as String but never subjected to code page conversions.	VARBINARY	32767	NO	Not padded to the dictionary defined maximum length.	RDMLX
NVarChar	Similar to String but data is handled as Unicode. This allows multiple languages to be used at execution time.	NVARCHAR	65535 characters	YES (but only when converted to native String)		RDMLX
Alpha	Constant length alphanumeric string with a dictionary defined maximum length.	CHAR (fixed length)	256	YES	Always padded with blanks to the dictionary defined maximum length.	Both
Date	Date in ISO format: YYYY-MM-DD	DATE	N/A	N/A		RDMLX
Time	Time is ISO format HH:MM:SS	TIME	N/A	N/A		RDMLX
DateTime	Date and Time in ISO format YYYY-MM-DD HH:MM:SS[.fffffffff] where the existence and length of the [.fffffffff] portion are definable.	DATETIME	29	N/A		RDMLX
Boolean	True/False	Decimal	N/A	N/A		RDMLX

Specialized Character and Binary Types (useable only in RDMLX programs)

Type	Description	Typically Stored in a DBMS as	Maximum Dictionary Definable Length	Typical DBMS Storage length used	Subject to Code Page Conversions	Important
Char	Exactly the same as String, except fixed length and DBMS storage implementation is usually CHAR.	CHAR	65535	Fixed length	YES
Binary	Exactly the same as VarBinary but DBMS implementation varies.	BINARY	32767	May be either Fixed or Variable.	NO	Databases that use fixed length column types will pad to the maximum length.
NChar	Exactly the same as NVarChar, except fixed length and DBMS storage implementation is usually NCHAR	NCHAR	65535	Fixed length	YES (but only when converted to native String)
CLOB	Character Large OBject	CLOB	Undefined	Varies according to content	YES	DBMS performance considerations may apply.
BLOB	Binary Large OBject	BLOB	Undefined	Varies according to content	NO	DBMS performance considerations may apply.

Rarely Used Numeric Types

Type

Description

Typical DBMS storage Type

Maximum Dictionary Definable Length

When to Use

Important

Useable in RDML or RDMLX Programs

Signed

Signed or Zoned decimal

DECIMAL

RDMLX programs: 63 digits of which up to 63 may be decimals

RDML programs: 30 digits of which up to 9 may be decimals

For programmatic numeric/character overlaying operations.

Signed is less efficient than Packed or Integer on mathematical operations.

Both

Float

Floating Point

FLOAT

Undefined.

Floating point numbers are approximations, not exact numbers.

When using non-LANSA defined DBMS tables only.

Hardware and compiler behaviors may vary.

RDMLX