Question

表1：

document.addEventListener("DOMContentLoaded", function(){
    var d = new Date(),
        display = document.getElementById("dateDisplay");
    display.innerHTML = d;
    display.style.color = "red";
});

我需要一个查询来按ITEMS [ID, PRODUCT_ID, RUN_ID, NAME, LOCATION, LAST_MODIFIED]和Product_ID对所有项目进行分组。

像这样：

Run_ID

但是，我还需要Select Product_ID, Run_ID, Count(ID) FROM ITEMS Group by Product_ID, Run_ID作为返回的每个组中的Location（最新）项目。

所以从本质上讲，我需要获得一列的最大值，但为该行返回另一列。

Answer 1

您可以使用window functions，// var commentId= "<?php echo $comment_id; ?>";和ROW_NUMBER实现此目的：

COUNT OVER

使用WITH Cte AS( SELECT *, cnt = COUNT(*) OVER(PARTITION BY Product_ID, Run_ID), rn = ROW_NUMBER() OVER(PARTITION BY Product_ID, Run_ID ORDER BY last_modified DESC) FROM ITEMS ) SELECT Product_ID, Run_ID, cnt, Location FROM Cte WHERE rn = 1：

JOIN

从SQL中的每个组行的max（）返回另一列

1 个答案: