项目练习：使用mybatis的foreach标签，实现union all的拼接语句

一、需求说明

在sql查询数据后，对数据分组统计。并最后进行总计。

二、需求分析

最终，我想用sql来实现这个统计和查询的功能。

那么，怎么又查询，又统计了？

就用到MySQL的union all关键字。

然后，通过mybatis把参数组装成list，传入，在利用foreach标签，循环拼接union all部分即可。

三、代码实现

Java代码

    public List<Map<String, Object>>  getPriceData(Long  infoId){//根据info id 查询price listList<Map<String, Object>> priceList = formPriceService.getVIds(infoId);List<Object> vids = new ArrayList<>();for (Map<String, Object> res : priceList) {vids.add(res.get("variety_id"));}Map<String, Object> params = new HashMap<>();params.put("infoId",infoId);params.put("vids",vids);List<Map<String, Object>> priceData = formPriceService.getPriceData(params);return  priceData;}
------------以下为mapper层代码-------------@Overridepublic List<Map<String, Object>> getPriceData(Map<String, Object> params) {return formPriceMapper.getPriceData(params);}@Overridepublic List<Map<String, Object>> getVIds(Long id) {return formPriceMapper.getVIds(id);}

xml代码
getVIds方法

<select id="getVIds" parameterType="Long" resultType="Map">SELECTdistinct price.variety_idFROM`rent_form_price` priceLEFT JOIN rent_form_info infoON	price.form_info_id = info.idLEFT JOIN rent_material_standard_temp stempON price.standard_id = stemp.idLEFT JOIN rent_material_variety_temp vtempON price.variety_id = vtemp.idLEFT JOIN rent_store_info storeON info.store_id = store.idWHERE price.form_info_id = #{formInfoId}</select>

getPriceData方法

    <select id="getPriceData" resultType="Map" parameterType="Map"><foreach collection="vids" item="vid" index="index" separator="union all">SELECTprice.variety_id,price.id,price.form_info_id,info.send_date,info.rent_begin_date,vtemp.variety_name,stemp.standard,price.number,price.rental_number,stemp.convert_amount,price.pound,store.store_name,price.note,stemp.rental_unitFROM`rent_form_price` priceLEFT JOIN rent_form_info info ON price.form_info_id = info.idLEFT JOIN rent_material_standard_temp stemp ON price.standard_id = stemp.idLEFT JOIN rent_material_variety_temp vtemp ON price.variety_id = vtemp.idLEFT JOIN rent_store_info store ON info.store_id = store.idWHEREprice.variety_id = #{vid}AND price.form_info_id = #{infoId}UNION ALLSELECT'','','','','',CONCAT(vtemp.variety_name,'小计:'),'',sum(price.number),sum(price.rental_number),'',sum(price.pound),'','',''FROMrent_form_price priceLEFT JOIN rent_material_variety_temp vtemp ON price.variety_id = vtemp.idWHEREprice.variety_id = #{vid}AND price.form_info_id = #{infoId}</foreach>UNION ALLSELECT'','','','','','本单总计:','',sum(price.number),sum(price.rental_number),'',sum(price.pound),'','',''FROMrent_form_price priceLEFT JOIN rent_material_variety_temp vtemp ON price.variety_id = vtemp.idWHEREform_info_id = #{infoId}</select>

四、报表效果