左外连接是否可以访问？

Question

以下查询在访问中不起作用。

SELECT Fields.FieldId, PrecisionSettings.DecimalPlaces 

    from Fields left outer join FieldGroup on Fields.FieldGroupId = FieldGroup.FieldGroupId

    left outer join Category on FieldGroup.CategoryId = Category.CategoryId

    left outer join PrecisionSettings on 

    Category.InputAttributesID=PrecisionSettings.AttributesID

它给出错误，因为查询表达式中缺少运算符。

Answer 1

在Access中，一次只能合并两个结果。要连接更多表，需要更多括号：

SELECT
    Fields.FieldId,
    PrecisionSettings.DecimalPlaces 
FROM
(
    (
        Fields
        LEFT OUTER JOIN FieldGroup ON Fields.FieldGroupId = FieldGroup.FieldGroupId
    )
    LEFT OUTER JOIN Category ON FieldGroup.CategoryId = Category.CategoryId
)
LEFT OUTER JOIN PrecisionSettings ON Category.InputAttributesID = PrecisionSettings.AttributesID