我已经尝试了在这种情况下返回值的所有公式，但不断收到错误消息，告诉我我的参数数量错误。这是我的查询：
SELECT [ER Root].[Network Indicator],
[ER Root].[Prov Indicator],
[ER Root].[Pos Indicator],
[ER].[ER Visit]
FROM [ER Root] LEFT JOIN ER ON ([ER Root].[Network Indicator] = ER.[Network Flag]) AND ([ER Root].[Pos Indicator] = ER.[POS Indicator]) AND ([ER Root].[Prov Indicator] = ER.[Category Indicator]);
我试过了：
SELECT [ER Root].[Network Indicator],
[ER Root].[Prov Indicator],
[ER Root].[Pos Indicator],
ISNULL([ER].[ER Visit],0) AS "ER Visit"
FROM [ER Root] LEFT JOIN ER ON ([ER Root].[Network Indicator] = ER.[Network Flag]) AND ([ER Root].[Pos Indicator] = ER.[POS Indicator]) AND ([ER Root].[Prov Indicator] …