mysql - 使用 UNION 对 SELECT COUNT 语句中的表进行 SUM 查询

Question

我目前正在尝试对 MySQL 语句的结果进行求和，该语句给出了几个不同表的行数。

我已经研究了 stackoverflow 中与此问题相关的所有解决方案。不幸的是，我无法找出适合我的情况的正确语法。

我的工作陈述以及未总结的结果:

SET @shipmentId=456;
SELECT
        (SELECT COUNT(*) FROM Table1 WHERE ShipmentID = @shipmentId)
        UNION ALL
        (SELECT COUNT(*) FROM Table2 WHERE ShipmentID = @shipmentId)
        UNION ALL
        (SELECT COUNT(*) FROM Table3 WHERE ShipmentID = @shipmentId)
        UNION ALL
        (SELECT COUNT(*)FROM Table4 WHERE ShipmentID = @shipmentId)
        UNION ALL
        (SELECT COUNT(*)FROM Table5 WHERE ShipmentID = @shipmentId);

在我看来，这应该是最接近正确的解决方案，但我不确定(尝试了很多变体):

SET @shipmentId=456;
SELECT SUM(MeasuredValues) FROM
    SELECT(
        (SELECT COUNT(*) FROM Table1 WHERE ShipmentID = @shipmentId) AS MeasuredValues
        UNION ALL
        (SELECT COUNT(*) FROM Table2 WHERE ShipmentID = @shipmentId) AS MeasuredValues
        UNION ALL
        (SELECT COUNT(*) FROM Table3 WHERE ShipmentID = @shipmentId) AS MeasuredValues
        UNION ALL
        (SELECT COUNT(*)FROM Table4 WHERE ShipmentID = @shipmentId) AS MeasuredValues
        UNION ALL
        (SELECT COUNT(*)FROM Table5 WHERE ShipmentID = @shipmentId)  AS MeasuredValues) t1;    

预先感谢您的帮助。

已经尝试过以下链接: StackOverFlow Solution1

StackOverFlow Solution2

Answer 1

您可以简单地总结您的选择:

SET @shipmentId=456;
SELECT
  (SELECT COUNT(*) FROM Table1 WHERE ShipmentID = @shipmentId)
+
  (SELECT COUNT(*) FROM Table2 WHERE ShipmentID = @shipmentId)
+
  (SELECT COUNT(*) FROM Table3 WHERE ShipmentID = @shipmentId)
+
  (SELECT COUNT(*) FROM Table4 WHERE ShipmentID = @shipmentId)
+
  (SELECT COUNT(*) FROM Table5 WHERE ShipmentID = @shipmentId);