在电源查询语言（M语言）中，我们如何添加自定义＆＃34;值＆＃34;和＆＃34;表＆＃34;手动列到表格？

Question

在电源查询中，如果我们从sql数据库获取数据，＆＃34; Value＆＃34;和＆＃34;表＆＃34;如果数据库中存在关系，则会自动创建列。

AFAIK＆＃34;表＆＃34;和＆＃34;价值＆＃34;分别表示一对多和多对一关系。

我的问题是我们的数据库中没有任何关系。因此PowerQuery无法自动生成这些列。 如果我知道主题表之间的关系，我该如何手动添加这些列？

我找到了返回Table对象的Table.NestedJoin函数（但性能很低，即使数据库中存在关系。）

但我找不到任何返回Value对象的函数（另一个表的记录）。

可能存在缺陷的其他解决方案;

1. 您可能会建议我在数据库中获取表格，并在Power BI中的“关系”部分（或Excel中的电源数据透视部分）中创建关系。但是我在power查询中需要这个Value对象，因为我想在加载表的所有行之前根据相关表过滤行。
2. 创建一个连接表的本机查询，这不是我的首选。
3. 创建Table对象而不是Value对象（我们确信只会有一条记录。）我仍然遇到Table.NestedJoin方法的性能问题。还有其他选择吗？

提前致谢...

Answer 1

Just today I had quite same issue with performance, but finally solved it. In my solution I work with views, but need to filter records coming.
When I use such a code:

let
    filter1 = 2016,
    filter2 = "SomeText",
    tbl = Sql.Database("MyServer","MyDB"){Schema="dbo",Item="MyTableOrView"}[Data],
    filteredTable = Table.SelectRows(tbl, each ([field1] = filter1) and ([field2] = filter2))
in
    filteredTable

it works slow. But if I try NestedJoin - it performs much better.

let
    Source = Table.FromColumns({{2016}, {"SomeText"}}, "filter1", "filter2"),
    tbl = Sql.Database("MyServer","MyDB"){Schema="dbo",Item="MyTableOrView"}[Data],
    filteredTable = Table.NestedJoin(tbl, {"field1", "field2"}, Source, {"filter1", "filter2"}, "NewColumn", JoinKind.Inner)
in
    filteredTable 

However, I noticed that even fastest design I got works slower than just a query that returns all ~~1300 rows from the view.

I have no SQL Profiler to track down what is exactly sent to the server, but it seems to me that query folding work when you use inner joins.

Try following: make 2 queries to 2 tables (no other actions!) and inner join them, then see if it works faster.