將case case語句轉換爲where子句中的邏輯運算符

Question

您可以幫助我將這段代碼轉換爲邏輯運算符，並使用'like'而不是'='因爲我知道將where語句放在where子句上效率不高。蒂亞！這是代碼。

Where 
(@reftype = '0' or 
    (@refnum = case @reftype when 'BN' then refBN when 'C' then refC when 'O' then refO else 'n/a' end) 
) 

Answer 1

更換

or @refnum = case @reftype when 'BN' then refBN when 'C' then refC when 'O' then refO else 'n/a' end) 

與

or (@reftype = 'BN' AND @refnum = refBN) 
or (@reftype = 'C' AND @refnum = refC) 
or (@reftype = 'O' AND @refnum = refO) 
or @refnum = 'n/a' 

Answer 2

您可以用這種方法把它轉變爲布爾邏輯：

WHERE @reftype = '0 'OR @refnum = 'n/a' 
OR (@reftype = 'BN' AND @refnum = refbn) 
OR (@reftype = 'C' AND @refnum = refc) 
OR (@reftype = 'O' AND @refnum = refo) 

但請注意，CASE在WHERE條本身並不是無效的。