声明标量和表格变量，只有 1 个在较低的查询中被识别

Question

有人可以向我解释为什么联合查询可以访问 orderRef 变量，而 orderId 不能吗？运行整个查询给出错误消息 "'where' operator: Failed to resolve scalar expression named 'orderId'"

** 我知道第二个 let 赋值就像我在第一个 2 个 let 赋值后立即使用 orderId 语句执行 orderId 一样，我将获得我想要的 orderId在最终联合查询中使用。

// <config>
let orderRef = "ABCDEF";
// </config>

// get orderId
let orderId = app('my-function').traces
| where message has orderRef
| order by timestamp asc
| extend msg=parse_json(substring(message, 6, strlen(message))) 
| project msg.OrderId;

union *,
    app('my-function').traces,
    app('my-function2').traces,
    app('my-function3').traces,
| where message has orderRef or message has orderId 
| project timestamp, cloud_RoleName, operation_Name, message;

Answer 1

toscalar()

let orderId = toscalar(app('my-function').traces
| where message has orderRef
| order by timestamp asc
| extend msg=parse_json(substring(message, 6, strlen(message))) 
| project msg.OrderId);

声明标量和表格变量，只有 1 个在较低的查询中被识别

Declare scalar and tabular variables, only 1 being recognised in lower query

azure

kql