我想从Twicat3 PLC环境中的查询结果构建SELECT语句。
当对变量进行硬编码时，查询可以正确执行，但是当从另一个查询的结果传递变量时，查询将无法执行。定义的数据类型是相同的。 InformationLog视图中的错误指示“词典中不存在给定的键”。使用第一个查询的结果执行查询时。
PROGRAM MAIN
VAR
conv_QueryDB : Query_tblConveyorQueue;
conv_queryRes : ARRAY [0..9] OF tblConveyorQueue;
conv_str_query : STRING(2000);
conv_query : WSTRING(2000);
conv_query1 : WSTRING(255) := "SELECT TOP 1 LEFT(AreaID,5) FROM ConveyorQueue WHERE CartonID = '";
conv_barcode : WSTRING(255) := "900981-1";
conv_query2 : WSTRING(255) := "' ORDER BY AreaID";
zone_QueryDB : Query_tblZoneMap;
zone_queryRes : ARRAY [0..18] OF tblZoneMap;
zone_str_query : STRING(2000);
zone_query : WSTRING(2000);
zone_query1 : WSTRING(255) := "SELECT transfer, zone, direction, neighborZone, deliveryLoc FROM tblZoneMap WHERE transfer = 1 AND zone = 0 AND deliveryLoc = '";
zone_dest : WSTRING(255);
zone_query2 : WSTRING(255) := "' ";
END_VAR
conv_query := WCONCAT(conv_query1, WCONCAT(conv_barcode, conv_query2));
conv_str_query := WSTRING_TO_STRING(conv_query);
conv_QueryDB(queryString := conv_str_query, dbConn := 2, bConnect := 1);
conv_queryRes := conv_QueryDB.queryResults;
zone_dest := STRING_TO_WSTRING(conv_queryRes[0].AreaID);
//zone_dest := "P1030"; //This works when uncommented??!!??
zone_query := WCONCAT(zone_query1, WCONCAT(zone_dest, zone_query2));
zone_str_query := WSTRING_TO_STRING(zone_query);
zone_QueryDB(queryString := zone_str_query, dbConn := 1, bConnect := 1);
zone_queryRes := zone_QueryDB.queryResults;
我希望将zone_dest作为硬编码值执行时与从conv_queryRes数组中提取时，zone_queryRes相同。我不确定这是否是数据类型问题。执行后，查询字符串似乎具有正确的语法。
-------------- EDIT -------------------------------- ---------------------------------
包括SQL功能块。
FUNCTION_BLOCK Query_tblZoneMap
VAR_INPUT
queryString : STRING(2000); //Select statement
dbConn : UDINT; //Int of connection configured in TF6420
bCONNECT : BOOL; //Rising trigger to connect to db. Need to make this re-fireable
END_VAR
VAR_OUTPUT
queryResults : ARRAY [0..18] OF tblZoneMap;
nError : INT;
END_VAR
VAR
fbSQLDatabase : FB_SQLDatabase(sNetID:='', tTimeout:=T#500MS);
fbSqlCommand : FB_SQLCommand(sNetID := '', tTimeout := T#500MS);
fbSQLResult : FB_SQLResult(sNetID:='', tTimeout:=T#500MS);
nState : INT;
R_TRIG1 : R_TRIG;
END_VAR
(*
Welcome to the QueryDB function block!
This function exists to query a database that is configured using the TF6420 Connectivity module.
When executed, it establishes a connection with the database, creates an instance of the FB_SQLCommand,
executes the instance of FB_SQLCommand, then reads the cached results using FB_SQLResult into the
queryResults array.
When results are received successfully, the database connection is closed.
*)
R_TRIG1(CLK:=bCONNECT);
IF R_TRIG1.Q AND nState = 0 THEN
nState := 1;
END_IF
CASE nState OF
0:(*Idle*)
IF bConnect THEN
bCONNECT := 0;
END_IF
1: // Connect to database
IF fbSqlDatabase.Connect(dbConn) THEN
IF fbSqlDatabase.bError THEN
nState := 255;
ELSE
nState := nState+1;
END_IF
END_IF
2: // Create a command reference
IF fbSqlDatabase.CreateCmd(ADR(fbSqlCommand)) THEN
IF fbSqlDatabase.bError THEN
nState := 255;
ELSE
nState := nState+1;
END_IF
END_IF
3://Execute SELECT Statement FB_SQLCommand.ExecuteDataReturn(pSQLCmd:= , cbSQLCmd:= , pSQLDBResult:= )
IF fbSQLCommand.ExecuteDataReturn(pSQLCmd:= ADR(queryString)
, cbSQLCmd:= SIZEOF(queryString)
, pSQLDBResult:= ADR(fbSqlResult)) THEN
IF fbSQLCommand.bError THEN
nState := 255;
ELSE
nState := nState + 1;
END_IF
END_IF
4://Read Results
IF fbSqlResult.Read(nStartIndex:= 0
,nRecordCount:= 19
,pData:= ADR(queryResults)
,cbData:= SIZEOF(queryResults)
,bWithVerifying:= FALSE
,bDataRelease:= FALSE) THEN
IF fbSqlResult.bError THEN
nState := 255;
ELSE
nState := nState+1;
END_IF
END_IF
5:// disconnect from database
IF fbSqlDatabase.Disconnect() THEN
IF fbSqlDatabase.bError THEN
nState := 255;
ELSE
nState := 0;
bConnect := 0;
END_IF
END_IF
255:
nError := 1; // If errored, check SQL logs.
bConnect := 0;
nState := 0;
END_CASE
答案 0 :(得分：0)
为什么首先使用WSTRING？ 使用普通的字符串，这样就不必来回转换，并且代码更易读。
如果将多个String并置在一起，请构建一个具有此功能的函数。 调用时看起来像这样：
F_CONCAT3(
zone_query1,
zone_dest,
zone_query2,
);
我建议您使用Beckhoff编码约定，以便其他开发人员也可以阅读您的代码：
您的代码将如下所示：
sConvQuery := F_CONCAT3(sConvQuery1, sConvBarcode, sConvQuery2);
//Use Enums instead of numbers
fbQueryDB(queryString := sConvQuery , dbConn := 2, bConnect := TRUE);
aConvQueryRes := fbQueryDB.queryResults;
sZoneDest := aConvQueryRes[0].AreaID;
sZoneQuery := F_CONCAT3(sZoneQuery1,sZoneDest,sZoneQuery2);
fbQueryDB(queryString := sZoneQuery, dbConn := 1, bConnect := TRUE);
aZoneQueryRes := fbQueryDB.queryResults;
能否请您发布zone_QueryDB功能块的代码？
答案 1 :(得分：0)
我还认为您应该按顺序放置查询，以避免Query_tblZoneMap功能块中发生任何冲突：
CASE nStep OF
eFIRST_QUERY:
sConvQuery := F_CONCAT3(sConvQuery1, sConvBarcode, sConvQuery2);
//Use Enums instead of numbers
fbQueryDB(queryString := sConvQuery , dbConn := 2, bConnect := TRUE);
nStep := eWAIT_FOR_FIRST_RESULT;
eWAIT_FOR_FIRST_RESULT:
IF NOT fbQueryDB.bBusy THEN
aConvQueryRes := fbQueryDB.queryResults;
nStep := eSECOND_QUERY;
END_IF
//Error handling
//ELSIF fbQueryDB.bError ...
eSECOND_QUERY:
sZoneDest := aConvQueryRes[0].AreaID;
sZoneQuery := F_CONCAT3(sZoneQuery1,sZoneDest,sZoneQuery2);
fbQueryDB(queryString := sZoneQuery, dbConn := 1, bConnect := TRUE);
nStep := eWAIT_FOR_SECOND_RESULT;
eWAIT_FOR_SECOND_RESULT:
IF NOT fbQueryDB.bBusy THEN
aZoneQueryRes := fbQueryDB.queryResults;
nStep := eCHECK_RESULT;
END_IF
//Error handling
//ELSIF fbQueryDB.bError ...
eCHECK_RESULT: //...
END_CASE