ReadStruct

This method reads a specified number of records from a database table with any table structure.

Syntax

METHOD ReadStruct : BOOL
VAR_INPUT
    hDBID: UDINT;
    sTableName: T_MaxString;
    pColumnNames: POINTER TO ARRAY [0..MAX_DBCOLUMNS] OF STRING(50);
    cbColumnNames: UDINT;
    sOrderByColumn: STRING(50);
    eOrderType: E_OrderType := E_OrderType.eOrder_ASC
    nStartIndex: UDINT;
    nRecordCount: UDINT;
    pData: POINTER TO BYTE;
    cbData: UDINT;
END_VAR

Inputs

Name	Type	Description
hDBID	UDINT	Indicates the ID of the database to be used.
sTableName	T_MaxString	Name of the table that is to be read.
pColumnNames	POINTER TO ARRAY [0..MAX_DBCOLUMNS] OF STRING(50)	Address of the array containing the column name to be read.
cbColumnNames	UDINT	Length of the column name array
sOrderByColumn	STRING(50)	Name the sorting column
eOrderType	E_OrderType	Sorting direction (ASC or DESC)
nStartIndex	UDINT	Indicates the index of the first record to be read.
nRecordCount	UDINT	Indicates the number of records to be read.
pData	POINTER TO BYTE	Address of the structure array into which the records are to be written.
cbData	UDINT	Indicates the size of the structure array in bytes.

Return value

Name	Type	Description
ReadStruct	BOOL	Displays the status of the method. Returns TRUE as soon as the method execution is finished, even in the event of an error.

Sample

VAR
    fbPLCDBRead    : FB_PLCDBReadEvt (sNetID := '', tTimeout := T#5S);
    myCustomStruct : ST_Record;
    tcMessage      : I_TcMessage;
END_VAR

TYPE ST_Record :
STRUCT
    nID        : LINT;
    dtTimestamp: DATE_AND_TIME;
    sName      : STRING;
    nSensor1   : LREAL;
    nSensor2   : LREAL;
END_STRUCT
END_TYPE

// set columnnames
ColumnNames[0] := 'ID';
ColumnNames[1] := 'Timestamp';
ColumnNames[2] := 'Name';
ColumnNames[3] := 'Sensor1';
ColumnNames[4] := 'Sensor2';

IF fbPLCDBRead.ReadStruct(
    hDBID:= 1, 
    sTableName:= 'MyTable_Struct', 
    pColumnNames:= ADR(ColumnNames), 
    cbColumnNames:= SIZEOF(ColumnNames), 
    sOrderByColumn:= ColumnNames[0], 
    eOrderType:= E_OrderType.DESC, 
    nStartIndex:= 0, 
    nRecordCount:= 1, 
    pData:= ADR(myCustomStruct), 
    cbData:= SIZEOF(myCustomStruct))
THEN
    IF fbPLCDBRead.bError THEN
        tcMessage:= fbPLCDBRead.ipTcResult;
        nState := 255; 
    ELSE
        nState := 0;
    END_IF
END_IF

Result in the PLC:

ReadStruct 3: