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Sql Avg delivers String instead of double [message #43439]

Wed, 30 July 2014 23:38

masu
Messages: 378
Registered: February 2006

Senior Member

Hi,

I noticed in one of my programs that with MySql the Avg() function on a field delivers a String type and not a double type result in response Value.

Here is the sql query I use:

SQL *	Select(	field1,
			Avg(field2), Count(field2),
			Avg(field3), Count(field3))
		.From(table1);

The DB schema is defined in a .sch file and all fields have sql type INT.
Surprisingly Count() in SQL[2] and SQL[4] delivers an expected numeric type (double) in this case which is converted to int automatically when using Value.

But I get a String in SQL[1] and SQL[3] which should also contain double type Value.

What is the reason for it to have String type instead of double?
Can somebody point me to the code location where SQL[] Value are assigned from DB response?

Regards
Matthias

931b81e7ea53320dccc37375b34b38c3

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Re: Sql Avg delivers String instead of double [message #43440 is a reply to message #43439]

Thu, 31 July 2014 15:27

mirek
Messages: 14257
Registered: November 2005

Ultimate Member

The problem might be in bool MySqlConnection::Execute();

See the switch there, I suspect that Avg returns some type that is not recognized there, so 'default' non-conversion to String takes the place.

After brief googling, could you please try to add FIELD_TYPE_NEW_DECIMAL to double section?

		for(int i = 0; i < fields; i++) {
			MYSQL_FIELD *field = mysql_fetch_field_direct(result, i);
			SqlColumnInfo& f = info[i];
			f.name = field->name;
			switch(field->type) {
			case FIELD_TYPE_TINY:
			case FIELD_TYPE_SHORT:
			case FIELD_TYPE_LONG:
			case FIELD_TYPE_INT24:
				f.type = INT_V;
				break;
			case FIELD_TYPE_LONGLONG:
			case FIELD_TYPE_DECIMAL:
			case FIELD_TYPE_FLOAT:
			case FIELD_TYPE_DOUBLE:
			case FIELD_TYPE_NEW_DECIMAL: // <<<<<<<<<<<<<<<<<<<<<<<<  THIS IS NEW...
				f.type = DOUBLE_V;
				break;
			case FIELD_TYPE_DATE:
				f.type = DATE_V;
				break;
			case FIELD_TYPE_DATETIME:
			case FIELD_TYPE_TIMESTAMP:
				f.type = TIME_V;
				break;
			case FIELD_TYPE_VAR_STRING:
			case FIELD_TYPE_STRING:
				convert[i] = true;
			default:
				f.type = STRING_V;
				break;
			}
			f.width = field->length;
			f.scale = f.precision = 0;
		}

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