Only the last GroupBy() call will be used

[ionling]

When you call GroupBy() multiple times, only the last one will be in the SQL.

Code:

func (sb *SelectBuilder) GroupBy(col ...string) *SelectBuilder {
	sb.groupByCols = col
	sb.marker = selectMarkerAfterGroupBy
	return sb
}

Why not:

func (sb *SelectBuilder) GroupBy(col ...string) *SelectBuilder {
	sb.groupByCols = append(sb.groupByCols, col...)
	sb.marker = selectMarkerAfterGroupBy
	return sb
}

[huandu]

Current API design enables us to update GROUP BY columns more than once. If we want to append more columns, we can simply append data to a cols slice and then call GroupBy(cols...).

[ionling]

The Where() method support multiple times calling, and I think we can keep the behavior of Where() and GroupBy() consistent. That will be better and convenient other than use append() function.