复杂删除SQL语句(Complex Delete SQL Statement)

 为什么删除语句有超出其选择对应项的限制？ 
 
 我没有被卡住，因为问题很容易解决，但我宁愿修复我的理解而不是继续使用变通办法。 
 
 例如，我有一个无向的边缘列表，其中包含字段V1和V2。 不幸的是，在创建表时，我引入了重复项（即V1 - > V2和V2 - > V1）。 为了识别重复，我运行了查询： 
 
SELECT t1.V1, t1.V2
FROM table t1
WHERE t1.V1 > t1.V2
    and EXISTS (
        SELECT *
        FROM table t2
        WHERE t2.V1 = t1.V2
          and t2.V2 = t1.V1 )
 
 因为这从表中返回了一组很好的行，我想我应该能够用delete替换select行并重新运行相同的查询。 然而，Sql server生气了，而是给了我红色字母。 关于语法和调整之后，关于绑定多部分标识符的事情。 
 
 我设法将select存储在一个表变量中并完成删除 - 这没关系，但是我的原始方法有什么问题，我可以用一个SQL语句完成它吗？ 

Why do delete statements have limitations beyond their select counterparts?
 
I am not stuck because the problem was easy enough to work around but I'd rather fix my understanding than continue using workarounds.
 
Case in point, I have an undirected, edge list with fields, V1 and V2. Unfortunately, when creating the table, I introduced duplicates (i.e. V1 -> V2 and V2 -> V1). To identify the dups, I ran the query:
 
SELECT t1.V1, t1.V2
FROM table t1
WHERE t1.V1 > t1.V2
    and EXISTS (
        SELECT *
        FROM table t2
        WHERE t2.V1 = t1.V2
          and t2.V2 = t1.V1 )
 
since this returned a nice set of rows from the table, I thought I should be able to replace the select line with delete and rerun the same query. Sql server however, got mad and gave me red letters instead. Once about syntax and after a tweak, something about binding multipart identifiers.
 
I managed to store the select in a table variable and get the delete done - which is ok, but what was wrong with my original approach and could I have done it with a single SQL statement?

原文：https://stackoverflow.com/questions/16285034