MySQL Pseudo-column

 
<!--Note:internal_name_trim is using pseudo-columns instead of data returned by the database--
<SelectID= "Listbystoreidandpartsnotrimandbrandname"Resultmap= "Productmap">SELECT product_id, Internal_name_trim from (<foreachCollection= "Productquerys"Item= "Productquery"Separator= "UNION All"Index= "Index">(select product_id, @myInternalName #{index} as Internal_name_trim from product, (select @myIn Ternalname#{index}:= #{productquery.internalnametrim}) r WHERE product_store_id = #{productstoreid} and PARTSN O_trim = #{productquery.partsnotrim} and brand_name = #{productquery.brandname} LIMIT 1)</foreach>) P</Select>

Note:1, limit 1 after the end, be sure to add parentheses, or become a piece of data2, the use of pseudo-column name can not be the same, otherwise all the last data will prevail

MySQL Pseudo-column