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如何优化嵌套条件SQL Server查询2008R2(How to optimize nested conditional SQL Server Query 2008R2)

if {condition1} = '0'
begin
    if  {condition2} = 'Yes'
        Begin
            Set @SQLQuery = @SQLQuery + ' AND  '
        end
    else 
        begin
            Set @SQLQuery = @SQLQuery + ' AND  '
        end
end


if {condition1} = '0'
begin
    if  {condition2} = 'Yes'
        Begin
            Set @SQLQuery = @SQLQuery + ' AND  '
        end
    else 
        begin
            Set @SQLQuery = @SQLQuery + ' AND  '
        end
end


原文：https://stackoverflow.com/questions/37066834
更新时间：2022-01-20 10:01

最满意答案

 如果两个列表都是有序的，您可以使用Zip扩展方法： 
 

tokens.Cast<TokensEnum>().Zip(names, (t, n) => Tuple.Create(t, n));

 

 这将返回IEnumerable<Tuple<TokensEnum, string>> 。 
 

 但正如Jon Skeet所暗示的那样 ，在这种情况下，做这样的事情可能会更容易： 
 

Enum.GetValues(typeof(TokensEnum))
    .Cast<TokensEnum>()
    .Select(t => Tuple.Create(t, t.ToString()));

 

 这将返回与上面相同的结果，但它将在一个步骤中完成。 
 

 既然你在评论中提到你想要一个Dictionary<string, TokensEnum> ，你可以使用这样的东西来构造它： 
 

Dictionary<string, TokensEnum> myDictionary = 
    Enum.GetValues(typeof(TokensEnum))
        .Cast<TokensEnum>()
        .ToDictionary(t => t.ToString());


If both lists are in order, you can use the Zip extension method:
 

tokens.Cast<TokensEnum>().Zip(names, (t, n) => Tuple.Create(t, n));

 

This will return an IEnumerable<Tuple<TokensEnum, string>>.
 

But as Jon Skeet suggests, in this case, it would probably be easier to do something like this:
 

Enum.GetValues(typeof(TokensEnum))
    .Cast<TokensEnum>()
    .Select(t => Tuple.Create(t, t.ToString()));

 

This will return the same result as above, but it will do it in a single step. 
 

Since you mentioned in your comments that you'd like to have a Dictionary<string, TokensEnum>, you can use something like this to construct it:
 

Dictionary<string, TokensEnum> myDictionary = 
    Enum.GetValues(typeof(TokensEnum))
        .Cast<TokensEnum>()
        .ToDictionary(t => t.ToString());

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