快速入門：執行你的第一個 DAX 查詢

在這個快速入門中，你會登入 Power BI，對語意模型執行 DAX 查詢，並將 Arrow 格式的回應反序列化成本地資料結構。

先決條件

• 一個至少有一個語意模型的 Power BI 工作空間。
• 在語意模型上建立並讀取權限。
• Microsoft Entra 應用程式註冊（或使用互動式認證進行測試）。

Python

• Python 3.10 或更新版本。

• 安裝依賴項

  pip install msal pyarrow pandas
  

C#

• .NET 8 SDK 或更新版本。

• 安裝依賴項

  dotnet add package Microsoft.Identity.Client
  dotnet add package Apache.Arrow
  

PowerShell

• PowerShell 7.4 或更新版本。

• 安裝 MSAL.PS 模組：

  Install-Module -Name MSAL.PS -Scope CurrentUser
  

1 - 認證

取得具有 https://analysis.windows.net/powerbi/api/.default 權限的持有者令牌。

Python

from msal import PublicClientApplication

client_id = "YOUR_APP_CLIENT_ID"
authority = "https://login.microsoftonline.com/YOUR_TENANT_ID"
scopes = ["https://analysis.windows.net/powerbi/api/.default"]

app = PublicClientApplication(client_id, authority=authority)
result = app.acquire_token_interactive(scopes=scopes)

access_token = result["access_token"]

C#

using Microsoft.Identity.Client;

var clientId = "YOUR_APP_CLIENT_ID";
var tenantId = "YOUR_TENANT_ID";
var scopes = new[] { "https://analysis.windows.net/powerbi/api/.default" };

var app = PublicClientApplicationBuilder
    .Create(clientId)
    .WithAuthority(AzureCloudInstance.AzurePublic, tenantId)
    .WithRedirectUri("http://localhost")
    .Build();

var result = await app.AcquireTokenInteractive(scopes).ExecuteAsync();
var accessToken = result.AccessToken;

PowerShell

$clientId = "YOUR_APP_CLIENT_ID"
$tenantId = "YOUR_TENANT_ID"
$scopes = @("https://analysis.windows.net/powerbi/api/.default")

$token = Get-MsalToken -ClientId $clientId -TenantId $tenantId -Scopes $scopes -Interactive
$accessToken = $token.AccessToken

2 - 執行 DAX 查詢

用簡單的 EVALUATE 語句向執行查詢箭頭端點發送 POST 請求。

Python

import io
import pyarrow as pa
import requests

group_id = "YOUR_WORKSPACE_ID"
dataset_id = "YOUR_DATASET_ID"

url = (f"https://api.powerbi.com/v1.0/myorg/groups/{group_id}"
       f"/datasets/{dataset_id}/executeDaxQueries")

headers = {
    "Authorization": f"Bearer {access_token}",
    "Content-Type": "application/json",
}

body = {"query": "EVALUATE TOPN(5, 'DimProduct')"}

response = requests.post(url, headers=headers, json=body)
response.raise_for_status()

reader = pa.ipc.open_stream(io.BytesIO(response.content))
table = reader.read_all()
df = table.to_pandas()

print(df)

C#

using System.Net.Http.Headers;
using Apache.Arrow;
using Apache.Arrow.Ipc;

var groupId = "YOUR_WORKSPACE_ID";
var datasetId = "YOUR_DATASET_ID";

var url = $"https://api.powerbi.com/v1.0/myorg/groups/{groupId}"
        + $"/datasets/{datasetId}/executeDaxQueries";

using var client = new HttpClient();
client.DefaultRequestHeaders.Authorization =
    new AuthenticationHeaderValue("Bearer", accessToken);

var body = new StringContent(
    """{"query": "EVALUATE TOPN(5, 'DimProduct')"}""",
    System.Text.Encoding.UTF8,
    "application/json");

var response = await client.PostAsync(url, body);
response.EnsureSuccessStatusCode();

using var stream = await response.Content.ReadAsStreamAsync();
using var reader = new ArrowStreamReader(stream);

var batch = await reader.ReadNextRecordBatchAsync();
Console.WriteLine($"Rows: {batch.Length}, Columns: {batch.ColumnCount}");

PowerShell

$groupId = "YOUR_WORKSPACE_ID"
$datasetId = "YOUR_DATASET_ID"

$url = "https://api.powerbi.com/v1.0/myorg/groups/$groupId" +
       "/datasets/$datasetId/executeDaxQueries"

$headers = @{
    "Authorization" = "Bearer $accessToken"
    "Content-Type"  = "application/json"
}

$body = @{ query = "EVALUATE TOPN(5, 'DimProduct')" } | ConvertTo-Json

$response = Invoke-WebRequest -Uri $url -Method Post -Headers $headers -Body $body

# Save the binary Arrow stream to a file for inspection
$arrowFile = "result.arrow"
[System.IO.File]::WriteAllBytes($arrowFile, $response.Content)
Write-Host "Arrow stream saved to $arrowFile ($($response.Content.Length) bytes)"

3 - 檢查結果

Python

# Print the Arrow schema (column names and types)
print(table.schema)

# Show the first few rows as a pandas DataFrame
print(df.head())

# Access a specific column
print(table.column("ProductName").to_pylist()[:5])

C#

// Print the schema (column names and types)
for (var i = 0; i < batch.Schema.FieldsList.Count; i++)
{
    var field = batch.Schema.FieldsList[i];
    Console.WriteLine($"  {field.Name}: {field.DataType}");
}

// Print the first row's values
for (var i = 0; i < batch.ColumnCount; i++)
{
    var column = batch.Column(i);
    Console.Write($"{batch.Schema.FieldsList[i].Name}=");
    Console.Write(column.GetType().GetMethod("GetValue")?.Invoke(column, new object[] { 0 }));
    Console.Write("  ");
}

PowerShell

# Use Python with pyarrow to read the saved Arrow file
python -c @"
import pyarrow as pa
reader = pa.ipc.open_stream('result.arrow')
table = reader.read_all()
print(table.schema)
print(table.to_pandas().head())
"@

清理資源

如果你只是為了測試而創建了Microsoft Entra應用程式註冊，請進入Azure入口網站並刪除它。 存取權憑證會自動過期，不需要手動撤銷。

相關內容

• 了解執行 DAX 查詢 API
• 教學：建立中階 DAX 查詢執行服務
• 教學：資料科學中的高容量Python萃取
• 執行 DAX 查詢 REST API 的最佳實務