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SQLSelect.FieldInfo Method (Typed)

X#
Retrieve information about or set an alias for the indicated column.

Namespace:  XSharp.VO.SDK
Assembly:  XSharp.VOSQLClasses (in XSharp.VOSQLClasses.dll) Version: 2.19
Syntax
 VIRTUAL METHOD FieldInfo(
	kFieldInfoType,
	uFieldPos,
	uFieldVal
) AS USUAL CLIPPER
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Parameters

kFieldInfoType (Optional)
Type: Usual
The type of information, as specified by the following constants:
uFieldPos (Optional)
Type: Usual
The name, number, or symbol representing the desired column.
uFieldVal (Optional)
Type: Usual
The alias name to be assigned to the column. This argument is only used if DB_ALIAS is specified for kColumnInfoType.

Return Value

Type: Usual
A value (whose data type depends on the value requested) if successful; otherwise, NIL.
Remarks
The SQLSelect:FieldInfo() method is used to retrieve information about a column, except if you specify kColumnInfoType to be DBS_ALIAS. You can then specify an alias for a column, which you can access by using the SQLColumn:AliasName property.
Tip Tip
The values in the table below exist both as DEFINEs and also as members of the DbFieldInfo enum.
You can see the numeric values of the defines in the documentation of this Enum.
ConstantsDescription
DBS_NAMEReturns the name of the field.
DBS_TYPEReturns the data type of the field.
DBS_LENReturns the length of the field.
DBS_DECReturns the number of decimal places for the field.
DBS_ALIAS Returns and optionally changes an alternate name (or alias) by which a field can be referenced (by default, same as DBS_NAME).
DBS_PROPERTIESReturns the number of properties defined for a field.
DBS_BLOB_DIRECT_LEN Returns the length of data in a BLOB as an unsigned long integer, without referencing a particular memo field. For strings, the return value is the length of the string in bytes; for arrays, it is the number of elements in the first dimension; for all other data types, it returns -1. With this constant, you must specify the BLOB using a numeric pointer obtained from DBServer:BLOBDirectPut(), DBServer:BLOBDirectImport(), or DBServer:FieldInfo(DBS_BLOB_POINTER, ... />).
DBS_BLOB_DIRECT_TYPE To determine the data type of BLOB data, without reference to a particular memo field, use DBServer:FieldInfo(DBS_BLOB_DIRECT_TYPE, ...). With this constant, you must specify the BLOB using a numeric pointer obtained from DBServer:BLOBDirectPut(), DBServer:BLOBDirectImport(), or DBServer:FieldInfo(DBS_BLOB_POINTER, ...).
See DBS_BLOB_TYPE for a table of possible return values.
DBS_BLOB_LEN Returns the length of the BLOB data in a memo field as an unsigned long integer. For strings, the return value is the length of the string in bytes; for arrays, it is the number of elements in the first dimension; for all other data types, it returns -1.
Tip Tip
DBServer:FieldInfo(DBS_BLOB_LEN, ...) has a performance advantage over the Len() function.
DBS_BLOB_POINTERReturns a numeric pointer to the BLOB data associated with a memo field.
DBS_BLOB_TYPE Unlike memo fields maintained in .DBT files, BLOB files allow you to store many different types of data in memo fields. However, the standard functions for determining data types, such as ValType(), simply treat BLOB fields as regular memo fields. To determine the actual type of BLOB data stored in a memo field, use DBServer:FieldInfo(DBS_BLOB_TYPE, ...). The data type of the return value is string and can be interpreted using this table:
ReturnsMeaning
?Blank (empty/uninitialized field)
AArray
CString
DDate
EError
LLogical
NNumeric
UUndefined (NIL was stored)
DBS_USERStart of user defined DBS_ values.
Tip Tip
DBS_USER is a constant that returns the minimum value that third-party RDD developers can use for defining new properties. Values less than DBS_USER are reserved for X# development.
See Also