@Override
public boolean visit(SQLSelectGroupByClause x) {
	result.getMergeContext().increGroupByCount();
	List<String> groupByColumns = new ArrayList<String>();
	List<SQLExpr> items = x.getItems();

	for (SQLExpr expr : items) {
		groupByColumns.add(((SQLName) expr).getSimpleName());
	}

	result.getMergeContext().setGroupByColumns(groupByColumns);
	return true;
}
 

private void findGroupBy(MySqlSelectQueryBlock query, Select select) throws SqlParseException {
    SQLSelectGroupByClause groupBy = query.getGroupBy();

    //modified by xzb group by 增加Having语法
    if (null != query.getGroupBy() && null != query.getGroupBy().getHaving()) {
        select.setHaving(query.getGroupBy().getHaving().toString());
    }

    SQLTableSource sqlTableSource = query.getFrom();
    if (groupBy == null) {
        return;
    }
    List<SQLExpr> items = groupBy.getItems();

    List<SQLExpr> standardGroupBys = new ArrayList<>();
    for (SQLExpr sqlExpr : items) {
        //todo: mysql expr patch
        if (sqlExpr instanceof MySqlOrderingExpr) {
            MySqlOrderingExpr sqlSelectGroupByExpr = (MySqlOrderingExpr) sqlExpr;
            sqlExpr = sqlSelectGroupByExpr.getExpr();
        }
        if ((sqlExpr instanceof SQLParensIdentifierExpr || !(sqlExpr instanceof SQLIdentifierExpr || sqlExpr instanceof SQLMethodInvokeExpr)) && !standardGroupBys.isEmpty()) {
            // flush the standard group bys
            // zhongshu-comment 先将standardGroupBys里面的字段传到select对象的groupBys字段中，然后给standardGroupBys分配一个没有元素的新的list
            select.addGroupBy(convertExprsToFields(standardGroupBys, sqlTableSource));
            standardGroupBys = new ArrayList<>();
        }

        if (sqlExpr instanceof SQLParensIdentifierExpr) {
            // single item with parens (should get its own aggregation)
            select.addGroupBy(FieldMaker.makeField(((SQLParensIdentifierExpr) sqlExpr).getExpr(), null, sqlTableSource.getAlias()));
        } else if (sqlExpr instanceof SQLListExpr) {
            // multiple items in their own list
            SQLListExpr listExpr = (SQLListExpr) sqlExpr;
            select.addGroupBy(convertExprsToFields(listExpr.getItems(), sqlTableSource));
        } else {
            // everything else gets added to the running list of standard group bys
            standardGroupBys.add(sqlExpr);
        }
    }
    if (!standardGroupBys.isEmpty()) {
        select.addGroupBy(convertExprsToFields(standardGroupBys, sqlTableSource));
    }
}