Revert "Add column default attribute"

@@ -104,11 +104,7 @@ func getColumnAddQuery(al *alias, fi *fieldInfo) string {
 		typ += " " + "NOT NULL"
 	}
 
-	return fmt.Sprintf("ALTER TABLE %s%s%s ADD COLUMN %s%s%s %s %s", 
-		Q, fi.mi.table, Q, 
-		Q, fi.column, Q, 
-		typ, getColumnDefault(fi),
-	)
+	return fmt.Sprintf("ALTER TABLE %s%s%s ADD COLUMN %s%s%s %s", Q, fi.mi.table, Q, Q, fi.column, Q, typ)
 }
 
 // create database creation string.
@@ -159,9 +155,6 @@ func getDbCreateSql(al *alias) (sqls []string, tableIndexes map[string][]dbIndex
 				//if fi.initial.String() != "" {
 				//	column += " DEFAULT " + fi.initial.String()
 				//}
-				
-				// Append attribute DEFAULT
-				column += getColumnDefault(fi)
 
 				if fi.unique {
 					column += " " + "UNIQUE"
@@ -246,42 +239,3 @@ func getDbCreateSql(al *alias) (sqls []string, tableIndexes map[string][]dbIndex
 
 	return
 }
-
-
-// Get string value for the attribute "DEFAULT" for the CREATE, ALTER commands
-func getColumnDefault(fi *fieldInfo) string {
-	var (
-		v, t, d        string
-	)
-	
-	t = " DEFAULT '%s' "
-
-	// These defaults will be useful if there no config value orm:"default" and NOT NULL is on
-	switch fi.fieldType {
-		case TypeDateField:
-			d = "0000-00-00"
-			
-		case TypeDateTimeField:
-			d = "0000-00-00 00:00:00"
-	
-		case TypeBooleanField, TypeBitField, TypeSmallIntegerField, TypeIntegerField,
-		TypeBigIntegerField, TypePositiveBitField, TypePositiveSmallIntegerField, 
-		TypePositiveIntegerField, TypePositiveBigIntegerField, TypeFloatField,
-		TypeDecimalField:
-			d = "0"
-	}
-	
-	if fi.colDefault {
-		if !fi.initial.Exist() {
-			v = fmt.Sprintf(t, "")
-		} else {
-			v = fmt.Sprintf(t, fi.initial.String())
-		}
-	} else {
-		if !fi.null {
-			v = fmt.Sprintf(t, d)
-		}
-	}
-	
-	return v
-}

@@ -116,7 +116,6 @@ type fieldInfo struct {
 	null                bool
 	index               bool
 	unique              bool
-	colDefault          bool
 	initial             StrTo
 	size                int
 	auto_now            bool
@@ -281,11 +280,6 @@ checkType:
 	fi.pk = attrs["pk"]
 	fi.unique = attrs["unique"]
 
-	// Mark object property if there is attribute "default" in the orm configuration
-	if _, ok := tags["default"]; ok {
-		fi.colDefault = true
-	}
-
 	switch fieldType {
 	case RelManyToMany, RelReverseMany, RelReverseOne:
 		fi.null = false