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you don't need to program a DLL, you can use existing.
for example MySQL:
Code:
#import "libmysql.dll"
int mysql_init(int db);
int mysql_errno(int TMYSQL);
int mysql_real_connect( int TMYSQL,string host,string user,string password, string DB,int port,int socket,int clientflag);
int mysql_real_query(int TMSQL,string query,int length);
void mysql_close(int TMSQL);
#import
int mysql;
int init(){
//----
mysql=mysql_init(mysql);
if (mysql!=0) Print("allocated");
string host="localhost";
string user="user";
string password="pwd";
string DB="mt4";
int clientflag=0;
int port=3306;
string socket="";
int
res=mysql_real_connect(mysql,host,user,password,DB,port,socket,clientflag);
int err=GetLastError();
if (res==mysql) Print("connected");
else Print("error=",mysql," ",mysql_errno(mysql)," ");
return(0);
}
//+------------------------------------------------------------------+
//| expert deinitialization function |
//+------------------------------------------------------------------+
int deinit()
{
//----
mysql_close(mysql);
//----
return(0);
}
int start()
{
string query="";
int length=0;
query=StringConcatenate("insert into ticks(margin,freemargin,date,ask,bid,symbol,equity) values(",AccountMargin(),",",AccountFreeMargin(),",\"",TimeToStr(CurTime(),TIME_DATE|TIME_SECONDS),"\",",NormalizeDouble(Ask,4),",",NormalizeDouble(Bid,4),",\"",Symbol(),"\",",AccountEquity(),");");
length=StringLen(query);
mysql_real_query(mysql,query,length);
int myerr=mysql_errno(mysql);
if (myerr>0)Print("error=",myerr);
}
hope this helps.
read also MySQL documentation for DLL usage.
for libmysql.dll look in "lib" subfolder of your mysql installation.
there is one problem though as metatrader can get only scalar datatypes from DLLs.
DDL and DML SQL statements work just fine, but if you need to read something from database with SELECT, it is not so trivial as result is in memory as some structure, which can not be read in MQ4.
to override this I had to output query result to a file and then read it in MQ4:
Code:
int GetClientTrades() {
FileDelete(queryFile);
string query="SELECT * INTO OUTFILE \'"+queryPFile+"\' FIELDS TERMINATED BY \';\' LINES TERMINATED BY \'\n\'FROM clients_trades;";
Print(query);
int length=StringLen(query);
mysql_real_query(mysql,query,length);
int myerr=mysql_errno(mysql);
if (myerr>0) Print("error=",myerr);
int handle,res,size,i;
ArrayResize(clientTrades,0);
handle=FileOpen(queryFile,FILE_CSV|FILE_READ);
if(handle<1) {
Print("File " + queryFile + " not found, the last error is ", GetLastError());
return(0);
}
while (!FileIsEnding(handle)) {
size++;
ArrayResize(clientTrades,size);
clientTrades[size-1][0]=FileReadNumber(handle);
clientTrades[size-1][1]=FileReadNumber(handle);
clientTrades[size-1][2]=FileReadNumber(handle);
clientTrades[size-1][3]=FileReadNumber(handle);
clientTrades[size-1][4]=FileReadNumber(handle);
clientTrades[size-1][5]=FileReadNumber(handle);
clientTrades[size-1][6]=FileReadNumber(handle);
clientTrades[size-1][7]=FileReadNumber(handle);
clientTrades[size-1][8]=FileReadNumber(handle);
clientTrades[size-1][9]=FileReadNumber(handle);
}
ArrayResize(clientTrades,size-1);
size--;
//if (clientTrades[size-1][0]==0.0) ArrayResize(clientTrades,size-1);
FileClose(handle);
return(1);
}
sorry to bring up an older thread but I have successfully connected and inserted data into a mysql database via the EA but I can't seem to figure out your code to SELECT data. I copied the function but it came up with a lot of errors.
Linear Mode
