Question

嘿伙计我有一些查询是由活动记录动态生成的，出于性能原因，我需要将它们合并在一起并一次性发送给MSSQL。

我尝试了以下内容，它在postgresql中运行良好，但我无法在MSSQL中使用它。

(SELECT  [panels].* FROM [panels] WHERE [panels].[environment_id] = 14 AND [panels].[agglo_code_id] = 23 AND [panels].[advert_area_id] = 161 AND [panels].[product_id] = 25 AND (NOT EXISTS(SELECT 1 FROM campaign_search_panels WHERE campaign_search_panels.panel_id = panels.panel_id AND campaign_search_panels.campaign_id = 65)) AND (NOT EXISTS(SELECT 1 FROM "AIDAAU_Avails" WHERE "AIDAAU_Avails"."PanelID" = panels.panel_uid AND "AIDAAU_Avails"."TillDate" >= '08-21-2017' AND "AIDAAU_Avails"."FromDate" <= '09-03-2017'))  ORDER BY [panels].[random_order] ASC OFFSET 0 ROWS FETCH NEXT 3 ROWS ONLY)
UNION ALL
(SELECT  [panels].* FROM [panels] WHERE [panels].[environment_id] = 14 AND [panels].[agglo_code_id] = 23 AND [panels].[advert_area_id] = 136 AND [panels].[product_id] = 25 AND (NOT EXISTS(SELECT 1 FROM campaign_search_panels WHERE campaign_search_panels.panel_id = panels.panel_id AND campaign_search_panels.campaign_id = 65)) AND (NOT EXISTS(SELECT 1 FROM "AIDAAU_Avails" WHERE "AIDAAU_Avails"."PanelID" = panels.panel_uid AND "AIDAAU_Avails"."TillDate" >= '08-21-2017' AND "AIDAAU_Avails"."FromDate" <= '09-03-2017'))  ORDER BY [panels].[random_order] ASC OFFSET 0 ROWS FETCH NEXT 2 ROWS ONLY)

现在我认为我已经发现了两个问题。如果我删除每个查询周围的括号，那么我靠近但它仍然抱怨ORDER。我有一种感觉，你只能在结果之后订购，但我不能控制每个单独的SQL查询如何组合在一起，只考虑我如何组合它们。理想情况下，我希望保持订单的能力，并为每个子查询设置限制条款。是否有任何简单的方法将它们组合在一起，以便它们可以在MSSQL中工作而不仅仅是postgres？

感谢您的帮助！

Answer 1

在UNION查询中，您只能有一个ORDER BY子句，它必须在最后：

SELECT * from <table1>
UNION ALL
SELECT * from <table2>
ORDER BY <col1>

您必须在顶部查询中删除该ORDER BY，它才能正常工作

Answer 2

如果要订购联合结果，则必须将结果放入CTE。像这样：

with cte_name as
(

select col_1, col_2, etc
from table

union all

select col_1, col_2, etc
from table_2

)

select col_1, col_2
from cte_name
order by col_1

如何在mssql中进行联合查询

2 个答案: