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harbour-core/harbour/doc/en/rddmisc.txt
2000-08-02 00:20:58 +00:00

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/*
* $Id$
*/
/*
* The following parts are Copyright of the individual authors.
* www - http://www.harbour-project.org
*
* Copyright 1999 Luiz Rafael Culik <culik@sl.conex.net>
* DB*() documentation
* ORD*() documentation
* RDD*() documentation
*
* See doc/license.txt for licensing terms.
*
*/
/* $DOC$
* $FUNCNAME$
* AFIELDS()
* $CATEGORY$
* Database
* $ONELINER$
* Fills referenced arrays with database field information
* $SYNTAX$
* AFields(<aNames>[,<aTypes>][,<aLen>][,<aDecs>]) --> <nFields>
* $ARGUMENTS$
* <aNames> Array of field names
*
* <aTypes> Array of field names
*
* <aLens> Array of field names
*
* <aDecs> Array of field names
* $RETURNS$
* <nFields> Number od fields in a database or work area
* $DESCRIPTION$
* This function will fill a series of arrays with field
* names,field types,field lenghts, and number of field
* decimal positions for the currently selected or designed
* database. Each array parallels the different descriptors
* of a file's structure.The first array will consist of the
* names of the fields in the current work area.All other arrays
* are optional and will be filled with the corrensponding data.
* This function will return zero if no parameters are specified
* or if no database is avaliable in the current work area.Otherwise,
* the number of fields or the lenght of the shortest array argument,
* witchever is smaller, will be returned.
* $EXAMPLES$
* FUNCTION Main()
* LOCAL aNames:={},aTypes:={},aLens:={},aDecs:={},nFields:=0
*
* USE Test
*
* dbGoTop()
* nFields:=aFields(aNames,aTypes,aLens,aDecs)
*
* ? "Number of fields", nFields
*
* RETURN NIL
* $STATUS$
* R
* $COMPLIANCE$
* AFIELDS() is fully CA-Clipper compliant.
* $FILES$
* Library is rdd
* $END$
*/
/* $DOC$
* $FUNCNAME$
* ALIAS()
* $CATEGORY$
* Database
* $ONELINER$
* Returns the alias name of a work area
* $SYNTAX$
* Alias([<nWorkArea>]) --> <cWorkArea>
* $ARGUMENTS$
* <nWorkArea> Number of a work area
* $RETURNS$
* <cWorkArea> Name of alias
* $DESCRIPTION$
* This function returns the alias of the work area indicated by <nWorkArea>
* If <nWorkArea> is not provided, the alias of the current work area is
* returned.
* $EXAMPLES$
* FUNCTION Main()
*
* USE Test
* select 0
* qOut( IF(Alias()=="","No Name",Alias()))
* Test->(qOut(Alias())
* qOut(Alias(1))
*
* RETURN NIL
* $STATUS$
* R
* $COMPLIANCE$
* ALIAS() is fully CA-Clipper compliant.
* $FILES$
* Library is rdd
* $SEEALSO$
* DBF()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* BOF()
* $CATEGORY$
* Database
* $ONELINER$
* Test for the beggining-of-file condition
* $SYNTAX$
* BOF() --> <lBegin>
* $RETURNS$
* BOF() Logical true (.T.) or false (.F.)
* $DESCRIPTION$
* This function determines if the beggining of the file marker has been
* reached. If so, the function will return a logical true (.T.); otherwise,
* a logical false(.F.) will be returned.
* By default, BOF() will apply to the currently selected database unless
* the function is preceded by an alias
* $EXAMPLES$
* FUNCTION Main()
* USE Tests NEW
* DBGOTOP()
* ? "Is Eof()",EOF()
* DBGOBOTTOM()
* ? "Is Eof()",EOF()
* USE
* RETURN NIL
* $STATUS$
* R
* $COMPLIANCE$
* BOF() is fully CA-Clipper compliant.
* $FILES$
* Library is rdd
* $SEEALSO$
* EOF(),FOUND(),LASTREC()
* $END$
*/
/* $DOC$
* $COMMANDNAME$
* ZAP
* $CATEGORY$
* Command
* $ONELINER$
* Remove all records from the current database file
* $SYNTAX$
* ZAP
* $DESCRIPTION$
* This command removes all of the records from the database in the
* current work area.This operation also updates any index file in
* use at the time of this operation.In addition, this command removes
* all items within an associated memo file.
* In a network enviroment,any file that is about to be ZAPped must
* be used exclusively.
* $EXAMPLES$
* USE Tests NEW index Tests
* ZAP
* USE
* $STATUS$
* R
* $COMPLIANCE$
* This command is CA Clipper compliant
* $SEEALSO$
* DELETE,PACK,USE
* $END$
*/
/* $DOC$
* $FUNCNAME$
* DELETED()
* $CATEGORY$
* Database
* $ONELINER$
* Tests the record's deletion flag.
* $SYNTAX$
* DELETED() --> lDeleted
* $RETURNS$
* DELETED() return a logical true (.T.) or false (.F.).
* $DESCRIPTION$
* This function returns a logical true (.T.) is the current record in the
* selected or designated work area ha ben marked for deletion.If not, the
* function will return a logical false (.F.).
* $EXAMPLES$
* FUNCTION Main()
* USE Test New
* DBGOTO()
* DBDELETE()
* ? "Is Record Deleted",Test->(DELETED())
* DBRECALL()
* USE
* RETURN NIL
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* DBDELETE()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* EOF()
* $CATEGORY$
* Database
* $ONELINER$
* Test for end-of-file condition.
* $SYNTAX$
* EOF() --> <lEnd>
* $RETURNS$
* <lEnd> A logical true (.T.) or false (.F.)
* $DESCRIPTION$
* This function determines if the end-of-file marker has been reached.
* If it has, the function will return a logical true (.T.); otherwise
* a logical false (.F.) will be returnd
* $EXAMPLES$
* FUNCTION Main()
* USE Tests NEW
* DBGOTOP()
* ? "Is Eof()",EOF()
* DBGOBOTTOM()
* ? "Is Eof()",EOF()
* USE
* RETURN NIL
* $STATUS$
* R
* $COMPLIANCE$
* EOF() is fully CA-Clipper compliant.
* $FILES$
* Library is rdd
* $SEEALSO$
* BOF(),FOUND(),LASTREC()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* FCOUNT()
* $CATEGORY$
* Database
* $ONELINER$
* Counts the number of fields in an active database.
* $SYNTAX$
* FCOUNT() --> nFields
* $RETURNS$
* <nFields> Return the number of fields
* $DESCRIPTION$
* This function returns the number of fields in the current or designated
* work area.If no database is open in this work area, the function will
* return 0.
* $EXAMPLES$
* FUNCTION Main()
* USE Tests NEW
* ? "This database have ",Tests->(FCOUNT()),"Fields"
* USE
* RETURN Nil
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* FIELDNAME(),TYPE()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* FIELDGET()
* $CATEGORY$
* Database
* $ONELINER$
* Obtains the value of a specified field
* $SYNTAX$
* FIELDGET(<nField>) --> ValueField
* $ARGUMENTS$
* <nField> Is the numeric field position
* $RETURNS$
* <ValueField> Any expression
* $DESCRIPTION$
* This function returns the value of the field at the <nField>th location
* in the selected or designed work area.If the value in <nField> does not
* correspond to n avaliable field position in this work area, the function
* will return a NIL data type.
* $EXAMPLES$
* FUNCTION Main()
* USE Test NEW
* ? Test->(FieldGet(1))
* USE
* RETURN NIL
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper Compliant.
* $FILES$
* Library is rdd
* $SEEALSO$
* FIELDPUT()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* FIELDNAME()
* $CATEGORY$
* Database
* $ONELINER$
* Return the name of a field at a numeric field location.
* $SYNTAX$
* FIELDNAME/FIELD(<nPosition>) --> cFieldName
* $ARGUMENTS$
* <nPosition> Field order in the database.
* $RETURNS$
* <cFieldName> returns the field name.
* $DESCRIPTION$
* This function return the name of the field at the <nPosition>th position.
* If the numeric value passed to this function does not correspond to an
* existing field in the designated or selected work area,this function
* will return a NULL byte.
* $EXAMPLES$
* FUNCTION Main()
* LOCAL x
* USE Tests NEW
* FOR x := 1 to Tests->(FCOUNT())
* ? "Field Name",FieldName(x)
* NEXT
* USE
* RETURN Nil
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compatible.
* $FILES$
* Library is rdd
* $SEEALSO$
* DBSTRUCT(),FCOUNT(),LEN(),VALTYPE()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* FIELDPOS()
* $CATEGORY$
* Database
* $ONELINER$
* Return the ordinal position of a field.
* $SYNTAX$
* FIELDPOS(<cFieldName>) --> nFieldPos
* $ARGUMENTS$
* <cFieldName> Name of a field.
* $RETURNS$
* <nFieldPos> is ordinal position of the field.
* $DESCRIPTION$
* This function return the ordinal position of the specified field <cField>
* in the current or aliased work areaIf there isn't field under the name
* of <cField> or of no database is open in the selected work area, the func-
* tion will return a 0.
* $EXAMPLES$
* FUNCTION Main()
* USE Test NEW
* ? Test->(FIELDPOS("ID"))
* USE
* RETURN NIL
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compliant.
* $FILES$
* Library is rdd
* $SEEALSO$
* FIELDGET(),FIELDPUT()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* FIELDPUT()
* $CATEGORY$
* Database
* $ONELINER$
* Set the value of a field variable
* $SYNTAX$
* FIELDPUT(<nField>, <expAssign>) --> ValueAssigned
* $ARGUMENTS$
* <nField> The field numeric position
*
* <expAssign> Expression to be assigned to the specified field
* $RETURNS$
* <ValueAssigned> Any expression
* $DESCRIPTION$
* This function assings the value in <expAssing> to the <nField>th
* field in the current or designated work area.If the operation is
* successful,the return value of the function will be the same value
* assigned to the specified field.If the operation is not successful,
* the function will return a NIL data type
* $EXAMPLES$
* USE Tests New
* FIELDPUT(1,"Mr. Jones")
* USE
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compatible.
* $FILES$
* Library is rdd
* $SEEALSO$
* FIELDGET()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* FLOCK()
* $CATEGORY$
* Database
* $ONELINER$
* Locks a file
* $SYNTAX$
* FLOCK() --> lSuccess
* $RETURNS$
* <lSuccess> A true (.T.) value, if the lock was successful;otherwise
* false (.F.)
* $DESCRIPTION$
* This function returns a logical true (.T.0 if a file lock is
* attempted and is successfully placed on the current or designated
* database.This function will also unlock all records locks placed
* by the same network station.
* $EXAMPLES$
* USE Tests New
* IF FLOCK()
* SUM Tests->Ammount
* ENDIF
* USE
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compatible
* $FILES$
* Library is rdd
* $SEEALSO$
* RLOCK()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* FOUND()
* $CATEGORY$
* Database
* $ONELINER$
* Determine the success of a previous search operation.
* $SYNTAX$
* FOUND() --> lSuccess
* $ARGUMENTS$
* None.
* $RETURNS$
* <lSuccess> A logical true (.T.) is successful;otherwise, false (.F.)
* $DESCRIPTION$
* This function is used to test if the previous SEEK,LOCATE,CONTINUE,
* or FIND operation was successful.Each wrk area has its own FOUND()
* flag,so that a FOUND() condition may be tested in unselected work
* areas by using an alias.
* $EXAMPLES$
* nId:=100
* USE Tests NEW INDEX Tests
* SEEK nId
* IF FOUND()
* ? Tests->Name
* ENDIF
* USE
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compatible
* $FILES$
* Library is rdd
* $SEEALSO$
* EOF()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* HEADER()
* $CATEGORY$
* Database
* $ONELINER$
* Return the length of a database file header
* $SYNTAX$
* HEADER() --> nBytes
* $RETURNS$
* <nBytes> The numeric size of a database file header in bytes
* $DESCRIPTION$
* This function returns the number of bytes in the header of the
* selected database ot the database in the designated work area.
*
* If used in conjunction with the LASTREC(),RECSIZE() and DISKSPACE()
* functions,this functions is capable of implementing a backup and
* restore routine.
* $EXAMPLES$
* USE Tests New
* ? Header()
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compatible
* $FILES$
* Library is rdd
* $SEEALSO$
* DISKSPACE(),LASTREC(),RECSIZE()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* LASTREC()
* $CATEGORY$
* Database
* $ONELINER$
* Returns the number of records in an active work area or database.
* $SYNTAX$
* LASTREC() | RECCOUNT()* --> nRecords
* $RETURNS$
* <nRecords > The number of records
* $DESCRIPTION$
* This function returns the number of records present in the database
* in the selected or designated work area.If no records are present
* the value of this function will be 0.Additionaly,if no database is
* in use in the selected or designated work area,this function will
* return a 0 value as well.
* $EXAMPLES$
* USE Tests NEW
* ? LASTREC(), RECCOUNT()
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA Clipper compatible
* $PLATFORMS$
* All
* $FILES$
* Library is rdd
* $SEEALSO$
* EOF()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* LUPDATE()
* $CATEGORY$
* Database
* $ONELINER$
* Yields the date the database was last updated.
* $SYNTAX$
* LUPDATE() --> dModification
* $ARGUMENTS$
* None
* $RETURNS$
* <dModification> The date of the last modification.
* $DESCRIPTION$
* This function returns the date recorded by the OS when the selected
* or designated database was last written to disk.This function will
* only work for those database files in USE.
* $EXAMPLES$
* Function Main
*
* Use Tests New
* ? Lupdate() // 04/25/2000
* Use
* Return Nil
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA Clipper compliant
* $PLATFORMS$
* All
* $FILES$
* Library is rdd
* $SEEALSO$
* FIELDNAME(),LASTREC(),RECSIZE()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* NETERR()
* $CATEGORY$
* Database
* $ONELINER$
* Tests the success of a network function
* $SYNTAX$
* NETERR([<lNewError>]) --> lError
* $ARGUMENTS$
* <lNewError> Is a logical Expression.
* $RETURNS$
* <lError> A value based on the success of a network operation or
* function.
* $DESCRIPTION$
* This function return a logical true (.T.) is a USE,APPEND BLANK, or
* a USE...EXCLUSIVE command is issue and fails in a network enviroment.
* In the case of USE and USE...EXCLUSIVE commands,a NETERR() value
* of .T. would be returned if another node of the network has the
* exclusive use of a file.And the case of the APPEND BLANK command,
* NETERR() will return a logical true (.T.) if the file or record
* is locked by another node or the value of LASTREC() has been advanced
* The value of NETERR() may be changed via the value of <lNewError>.
* This allow the run-time error-handling system to control the way
* certains errors are handled.
* $EXAMPLES$
* USE TEST NEW Index Test
* If !NetErr()
* Seek Test->Name="HARBOUR"
* If Found()
* ? Test->Name
* Endif
* Endif
* USE
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* FLOCK(),RLOCK()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* RECCOUNT()
* $CATEGORY$
* Database
* $ONELINER$
* Counts the number of records in a database.
* $SYNTAX$
* RECCOUNT()* | LASTREC() --> nRecords
* $ARGUMENTS$
* None.
* $RETURNS$
* <nRecords> The number of records
* $DESCRIPTION$*
* This function returns the number of records present in the database
* in the selected or designated work area.If no records are present
* the value of this function will be 0.Additionaly,if no database is
* in use in the selected or designated work area,this function will
* return a 0 value as well.
* $EXAMPLES$
* Use Test NEW
* USE Harbour NEW
* ? Reccount()
* ? Test->(RECCOUNT())
* CLOSE ALL
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is CA-Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* EOF(),LASTREC(),RECNO(),DBGOBOTTOM()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* RECNO()
* $CATEGORY$
* Database
* $ONELINER$
* Returns the current record number or identity.
* $SYNTAX$
* RECNO() --> Identity
* $ARGUMENTS$
* None.
* $RETURNS$
* RECNO() The record number or indentity
* $DESCRIPTION$
* This function returns the position of the record pointer in the
* currently selected ot designated work area.
* If the database file is empty and if the RDD is the traditional .DBF
* file,the value of this function will be 1.
* $EXAMPLES$
* USE Tests NEW
* DBGOTOP()
* RECNO() // Returns 1
* DBGOTO(50)
* RECNO() // Returns 50
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is Ca-Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* DBGOTO(),DBGOTOP(),DBGOBOTTOM(),LASTREC(),EOF(),BOF()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* RECSIZE()
* $CATEGORY$
* Database
* $ONELINER$
* Returns the size of a single record in an active database.
* $SYNTAX$
* RECSIZE() --> nBytes
* $ARGUMENTS$
* None.
* $RETURNS$
* <nBytes> The record size.
* $DESCRIPTION$
* This function returns the number os bytes used by a single record
* in the currently selected or designated database file.If no database
* is in use in this work area,the return value from this function
* will be 0.
* $EXAMPLES$
* USE Tests NEW
* DBGOTOP()
* RECSIZE() // Returns 1
* DBGOTO(50)
* RECSIZE()
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is Ca-Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* DISKSPACE(),FIELDNAME(),HEADER(),LASTREC()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* RLOCK()
* $CATEGORY$
* Database
* $ONELINER$
* Lock a record in a work area
* $SYNTAX$
* RLOCK() --> lSuccess
* $ARGUMENTS$
* None
* $RETURNS$
* RLOCK() True (.T.) if record lock is successful; otherwise, it
* returns false (.F.).
* $DESCRIPTION$
* This function returns a logical true (.T.) if an attempt to lock a
* specific record in a selected or designated work area is successful.
* It will yield a false (.F.) if either the file or the desired record
* is currently locked.
* A record that is locked remains locked until another RLOCK() is issued
* or until an UNLOCK command is executed.
* On a Network enviroment the follow command need that the record is
* locked:
*
* @...GET
*
* DELETE (single record)
*
* RECALL (single record)
*
* REPLACE (single record)
* $EXAMPLES$
* nId:=10
* USE TestId INDEX TestId NEW
* IF TestId->(DBSEEK(nId))
* IF TestId->(RLOCK())
* DBDELETE()
* ENDIF
* ENDIF
* USE
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is Ca-Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* FLOCK()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* SELECT()
* $CATEGORY$
* Database
* $ONELINER$
* Returns the work area number for a specified alias.
* $SYNTAX$
* SELECT([<cAlias>]) --> nWorkArea
* $ARGUMENTS$
* <cAlias> is the target work area alias name.
* $RETURNS$
* SELECT() returns the work area number.
* $DESCRIPTION$
* This function returns the work area number for the specified alias
* name <cAlias>.If no parameter is specified,the current work area will
* be the return value of the function.
* $EXAMPLES$
* USE TESTS NEW
* USE NAMES NEW
* cOldArea:=SELECT("NAMES")
* select TEST
* LIST
* SELECT cOldArea
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is Ca-Clipper compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* ALIAS(),USED()
* $END$
*/
/* $DOC$
* $FUNCNAME$
* USED()
* $CATEGORY$
* Database
* $ONELINER$
* Checks whether a database is in use in a work area
* $SYNTAX$
* USED() --> lDbfOpen
* $ARGUMENTS$
* None.
* $RETURNS$
* <lDbfOpen> True is a database is Used;otherwise False
* $DESCRIPTION$
* This function returns a logical true (.T.) if a database file is in
* USE in the current or designated work area. If no alias is specified
* along with this function , it will default to the currently selected
* work area.
* $EXAMPLES$
* Use TESTS NEW
* USE Names New
* ? USED() // .T.
* ? TESTS->(USED()) //.t.
* CLOSE
* ? USED() // .F.
* Select TESTS
* ? USED() //.T.
*
* $TESTS$
* $STATUS$
* R
* $COMPLIANCE$
* This function is Ca-clipper Compliant
* $FILES$
* Library is rdd
* $SEEALSO$
* ALIAS(),SELECT()
* $END$
*/
/* $DOC$
* $COMMANDNAME$
* PACK
* $CATEGORY$
* Command
* $ONELINER$
* Remove records marked for deletion from a database
* $SYNTAX$
* PACK
* $DESCRIPTION$
* This command removes records that were marked for deletion from the
* currently selected database.This command does not pack the contents
* of a memo field;those files must be packed via low-level fuctions.
*
* All open index files will be automatically reindexed once PACK command
* has completed its operation.On completion,the record pointer is placed
* on the first record in the database.
* $EXAMPLES$
* USE Tests NEW index Tests
* DBGOTO(10)
* DELETE NEXT 10
* PACK
* USE
* $STATUS$
* R
* $COMPLIANCE$
* This command is CA Clipper compliant
* $SEEALSO$
* DBEVAL(),DELETE,DELETED(),ZAP,RECALL
* $END$
*/