mysql - 程序中的替代方法mysql嵌套查询

Question

对程序中的mysql嵌套查询有什么建议吗？

CREATE DEFINER=`root`@`%` PROCEDURE `GET_PLACE_PARENT_CATEGORY`(IN paramCategoryId INT)
BEGIN
    SELECT pc.place_parent_category_id, (SELECT pcc.place_category FROM place_category  pcc WHERE pcc.place_category_id = pc.place_parent_category_id )
FROM place_category pc WHERE pc.place_category_id = paramCategoryId;
END

Answer 1

您的嵌套查询在同一张表上。你确定这是正确的吗？我相信您想要两个表之间的简单连接。可能是这样的：

SELECT pc.place_parent_category_id, pcc.place_category
FROM place_category pc left join place_parent_category as pcc on pcc.place_category_id = pc.place_parent_category_id WHERE pc.place_parent_category_id = paramCategoryId;