在网上看了很多教程，不是很明白多表查询究竟是怎么搞的：

/**根据数量来统计*/@Overridepublic List<InStockDetailPage> combobox2Sl( InStockDetailPage isp) {List<InStockDetailPage> nl = new ArrayList<InStockDetailPage>();StringBuffer sql = new StringBuffer();sql.append( "select d.incode from drp_instock d where d.status=1 ");if(isp.getCkid()!=null&&!isp.getCkid().equals("")){sql.append( " and d.rhck='"+isp.getCkid()+"' ");}if(isp.getJsr()!=null&&!isp.getJsr().equals("")){sql.append(" and d.jsr='"+isp.getJsr()+"' ");}if(isp.getRkstart()!=null&&!isp.getRkstart().equals("")){sql.append(" and d.indate >='"+isp.getRkstart()+"' ");}if(isp.getRkend()!=null&&!isp.getRkend().equals("")){sql.append(" and d.indate <='"+isp.getRkend()+"' ");}if(isp.getGys()!=null&&!isp.getGys().equals("")){sql.append( " and d.gys >='"+isp.getGys()+"' ");}String hql = "select t.gid gid,sum(t.num) tsum from drp_instockdetail t where 1=1 and t.inid in ("+sql.toString()+") group by t.gid";JdbcTemplate jt = goodsDao.getJdbcTemplate();List<Map<String, Object>> list=jt.queryForList(hql, new Object[]{});for (Map<String,Object> m :list) {InStockDetailPage isdp = new InStockDetailPage();isdp.setGid(m.get("gid").toString());int num = 0;try {num =Integer.parseInt(m.get("tsum").toString());} catch (Exception e) {num = 0;}isdp.setGname(goodsDao.get(Goods.class, isdp.getGid()).getName());isdp.setGcode(goodsDao.get(Goods.class, isdp.getGid()).getCode());isdp.setDid(UUID.randomUUID().toString());isdp.setTnum(num);nl.add(isdp);}return nl;}

@Overridepublic DataGrid datagrid2TabJe(InStockDetailPage isp) {DataGrid dg = new DataGrid();List<InStockDetailPage> nl = new ArrayList<InStockDetailPage>();StringBuffer sql = new StringBuffer();sql.append( "select d.incode from drp_instock d where d.status=1 ");if(isp.getCkid()!=null&&!isp.getCkid().equals("")){sql.append( " and d.rhck='"+isp.getCkid()+"' ");}if(isp.getJsr()!=null&&!isp.getJsr().equals("")){sql.append(" and d.jsr='"+isp.getJsr()+"' ");}if(isp.getRkstart()!=null&&!isp.getRkstart().equals("")){sql.append(" and d.indate >='"+isp.getRkstart()+"' ");}if(isp.getRkend()!=null&&!isp.getRkend().equals("")){sql.append(" and d.indate <='"+isp.getRkend()+"' ");}if(isp.getGys()!=null&&!isp.getGys().equals("")){sql.append( " and d.gys >='"+isp.getGys()+"' ");}String hql = "select t.gid gid,sum(t.lsum) msum from drp_instockdetail t where 1=1 and t.inid in ("+sql.toString()+") group by t.gid";JdbcTemplate jt = goodsDao.getJdbcTemplate();List<Map<String, Object>> list=jt.queryForList(hql, new Object[]{});for (Map<String,Object> m :list) {InStockDetailPage isdp = new InStockDetailPage();isdp.setGid(m.get("gid").toString());BigDecimal num = new BigDecimal(0);try {num =new BigDecimal(m.get("msum").toString());} catch (Exception e) {num =new BigDecimal(0);}isdp.setDid(UUID.randomUUID().toString());isdp.setMsum(num);nl.add(isdp);}double d = 0;for(InStockDetailPage i : nl){d += i.getMsum().doubleValue();}List<InStockDetailPage> nl2 = new ArrayList<InStockDetailPage>();for(InStockDetailPage i : nl){if(i.getMsum().doubleValue()>0){i.setSzbl(String.format("%.2f", i.getMsum().doubleValue()/d*100)+"%");}else{i.setSzbl("0%");}Goods g = goodsDao.get(Goods.class, i.getGid());i.setGname(g.getName());i.setGcode(g.getCode());nl2.add(i);}dg.setTotal(Long.valueOf(nl.size()));dg.setRows(nl2);return dg;}

@Overridepublic DataGrid datagrid2TabSl(InStockDetailPage isp) {DataGrid dg = new DataGrid();List<InStockDetailPage> nl = new ArrayList<InStockDetailPage>();StringBuffer sql = new StringBuffer();sql.append( "select d.incode from drp_instock d where d.status=1 ");if(isp.getCkid()!=null&&!isp.getCkid().equals("")){sql.append( " and d.rhck='"+isp.getCkid()+"' ");}if(isp.getJsr()!=null&&!isp.getJsr().equals("")){sql.append(" and d.jsr='"+isp.getJsr()+"' ");}if(isp.getRkstart()!=null&&!isp.getRkstart().equals("")){sql.append(" and d.indate >='"+isp.getRkstart()+"' ");}if(isp.getRkend()!=null&&!isp.getRkend().equals("")){sql.append(" and d.indate <='"+isp.getRkend()+"' ");}if(isp.getGys()!=null&&!isp.getGys().equals("")){sql.append( " and d.gys >='"+isp.getGys()+"' ");}String hql = "select t.gid gid,sum(t.num) tsum from drp_instockdetail t where 1=1 and t.inid in ("+sql.toString()+") group by t.gid";JdbcTemplate jt = goodsDao.getJdbcTemplate();List<Map<String, Object>> list=jt.queryForList(hql, new Object[]{});for (Map<String,Object> m :list) {InStockDetailPage isdp = new InStockDetailPage();isdp.setGid(m.get("gid").toString());int num = 0;try {num =Integer.parseInt(m.get("tsum").toString());} catch (Exception e) {num = 0;}isdp.setGname(goodsDao.get(Goods.class, isdp.getGid()).getName());isdp.setGcode(goodsDao.get(Goods.class, isdp.getGid()).getCode());isdp.setDid(UUID.randomUUID().toString());isdp.setTnum(num);nl.add(isdp);}double d = 0;for(InStockDetailPage i : nl){d += i.getTnum();}List<InStockDetailPage> nl2 = new ArrayList<InStockDetailPage>();for(InStockDetailPage i : nl){if(i.getTnum()>0){i.setSzbl(String.format("%.2f", i.getTnum()/d*100)+"%");}else{i.setSzbl("0%");}Goods g = goodsDao.get(Goods.class, i.getGid());i.setGname(g.getName());i.setGcode(g.getCode());nl2.add(i);}dg.setTotal(Long.valueOf(nl.size()));dg.setRows(nl2);return dg;}

好了，就这样吧，你若能懂，那就懂了，你若不能，我就自言自语了！