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Re: How to display fields from different tables in one SQLArray [message #19152 is a reply to message #19120]

Sat, 15 November 2008 15:02

mirek is currently offline

mirek
Messages: 13976
Registered: November 2005

Ultimate Member

sergeynikitin wrote on Thu, 13 November 2008 05:26

What do you mean? What is the difference between SQL and sql?

I mean that SQL is global variable (well, technically, it is more comlicated, but it behaves just like global variable).

And the inherent problem with global variables is that they are problem in reentrant code.

void Sum(int id) {
  return SQL % Select(SqlSum(MONEY)).From(TABLE).Where(ID == id);
}

void PrintSums() {
  SQL * Select(NAME, MONEY_ID).From(TABLE);
  while(SQL.Fetch())
     Print(SQL[NAME], Sum(SQL[MONEY_ID]);
}

I have made this bug way too many times -> that is why I always have to warn about fetching from SQL.

Quote:

	MySqlSession session;
	if(!session.Connect(app.mysql_username, app.mysql_password, app.mysql_database, app.mysql_server)) {
		printf("Can't connect with MySql\n");
		PromptOK(t_("Can't connect with MySql"));
		return;
	}
	mysql_set_character_set(session, "utf8");
	
	SQL = session;
	Sql sql(session);

This corrent and in fact, you do not need to repeat

Sql sql(session);

because

Sql sql;

is the same as

Sql sql(SQL.GetSession());

There are two purposes for SQL - to serve as simple cursor for inster/delete/update and inline fetches AND to represent default global database connection so that you do not need to repeat 'session' all the time.

Just do not do explicit fetches from it, because while technically possible, it is a sure way how to shoot you leg:)

Mirek

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[Message index]

		How to display fields from different tables in one SQLArray By: sergeynikitin on Mon, 20 October 2008 14:14
		Re: How to display fields from different tables in one SQLArray By: zsolt on Mon, 20 October 2008 14:20
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Mon, 20 October 2008 14:28
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Mon, 20 October 2008 14:55
		Re: How to display fields from different tables in one SQLArray By: zsolt on Mon, 20 October 2008 22:51
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Mon, 20 October 2008 23:00
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Mon, 20 October 2008 23:04
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sun, 02 November 2008 14:12
		Re: How to display fields from different tables in one SQLArray By: mirek on Sun, 02 November 2008 16:47
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sun, 02 November 2008 16:54
		Re: How to display fields from different tables in one SQLArray By: unodgs on Sun, 02 November 2008 19:09
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sun, 02 November 2008 19:41
		Re: How to display fields from different tables in one SQLArray By: unodgs on Sun, 02 November 2008 20:44
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sun, 02 November 2008 21:50
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sun, 02 November 2008 21:58
		Re: How to display fields from different tables in one SQLArray By: mirek on Sun, 02 November 2008 22:01
		Re: How to display fields from different tables in one SQLArray By: mirek on Sun, 02 November 2008 21:59
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sun, 02 November 2008 22:09
		Re: How to display fields from different tables in one SQLArray By: mirek on Wed, 12 November 2008 22:23
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Thu, 13 November 2008 11:26
		Re: How to display fields from different tables in one SQLArray By: mirek on Sat, 15 November 2008 15:02
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sat, 15 November 2008 15:48
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Fri, 20 March 2009 17:06
		Re: How to display fields from different tables in one SQLArray By: mirek on Sun, 02 November 2008 21:55
		Re: How to display fields from different tables in one SQLArray By: mr_ped on Fri, 20 March 2009 21:37
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Sat, 21 March 2009 08:04
		Re: How to display fields from different tables in one SQLArray By: sergeynikitin on Tue, 07 July 2009 09:47
		template + convert problem By: sergeynikitin on Sat, 19 September 2009 14:22
		Re: template + convert problem By: Zbych on Sat, 19 September 2009 19:30
		Re: template + convert problem By: andrei_natanael on Sat, 19 September 2009 19:59
		Re: template + convert problem By: sergeynikitin on Sat, 19 September 2009 22:45
		Re: template + convert problem By: sergeynikitin on Sat, 19 September 2009 22:37
		Re: template + convert problem By: Zbych on Sun, 20 September 2009 15:47
		Re: template + convert problem By: sergeynikitin on Mon, 21 September 2009 07:34
		Re: template + convert problem By: sergeynikitin on Thu, 30 April 2015 07:55

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