Question

SQL2008。我在表中有浮点值，需要重写以下规则集。规则在另一个表中。

但规则是分层的，即 - 我需要对主表中的每一行应用最严格的所有合适规则。

以下是示例...规则表（B和C可以是NULLS）

A    B    C    Value
1    2    3    100
1    2    NULL 80
1    NULL NULL 60

Main Table
A     B     C     Value OverridenValue
1     2     3     1     100
1     2     2     2     80
1     3     1     3     60
3     1     3     4     4    <- no override as no rule found
NULL  NULL  NULL  5     5    <- no override as no rule found

我需要一个标量函数，即fnGetOverridenValue（@A int，@ B int，@ C int）返回float

Answer 1

Select m.A, m.B, m.C, m.[Value],
  Case 
    When Not IsNull(r1.Value) Then r1.Value
    When Not IsNull(r2.Value) Then r2.Value
    When Not IsNull(r3.Value) Then r3.Value
    Else m.[Value]
  End as Overriddenvalue
From
  MainTable m
  Left Join RulesTable r1 on m.A=r1.A and m.B=r1.B and m.C=r1.C
  Left Join RulesTable r2 on m.A=r2.A and m.B=r2.B and r2.C is NULL
  Left Join RulesTable r3 on m.A=r3.A and r3.B is NULL and r3.C is NULL

Answer 2

在RulesTable中添加一个Priority列，其中第一个规则为1，依此类推。

select top 1 from RulesTable
where A=@A 
and (B=@B or @B is null and B is null)
and (C=@C or @C is null and C is null)
order by priority

SQL。分层应用业务规则

2 个答案: