mysql伪列

Posted 2020-09-22

 

 
<!-- NOTE:internal_name_trim使用的是伪列，而不是数据库返回的数据 -->
<select id="listByStoreIdAndPartsNoTrimAndBrandName" resultMap="productMap">
 SELECT
   product_id,
   internal_name_trim
 FROM (
   <foreach collection="productQuerys" item="productQuery"
   separator="UNION ALL" index="index">
     (SELECT
       product_id,
       @myInternalName#{index} as internal_name_trim
     FROM
     product,(SELECT @myInternalName#{index}:= #{productQuery.internalNameTrim}) r
     WHERE
     product_store_id = #{productStoreId}
     AND partsno_trim = #{productQuery.partsNoTrim}
     AND brand_name = #{productQuery.brandName}
     LIMIT 1)
   </foreach>
 ) p
 </select>

 

 

 

注意：

1、limit 1 结尾后，一定要加括号，否则变成一条数据

2、使用伪列的名称不能一样，否则都以最后那条数据为准