SQL / C＃ – UPSERT上的主键错误

更新 （简化问题，从问题中删除C＃）

在下列情况下，如何编写可以识别两行相同的UPSERT …

看看那里有一个\ b [退格]编码（奇怪的小角色）？ SQL认为这些是相同的。 虽然我的UPSERT将此视为新数据并尝试INSERT，其中应该有更新。

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//UPSERT INSERT INTO [table] SELECT [col1] = @col1, [col2] = @col2, [col3] = @col3, [col4] = @col4 FROM [table] WHERE NOT EXISTS -- race condition risk here? ( SELECT 1 FROM [table] WHERE [col1] = @col1 AND [col2] = @col2 AND [col3] = @col3) UPDATE [table] SET [col4] = @col4 WHERE [col1] = @col1 AND [col2] = @col2 AND [col3] = @col3 

Answer 1

您需要@符号，否则会触发C＃字符转义序列。

C＃定义了以下字符转义序列：

 \' - single quote, needed for character literals \" - double quote, needed for string literals \\ - backslash \0 - Unicode character 0 \a - Alert (character 7) \b - Backspace (character 8) \f - Form feed (character 12) \n - New line (character 10) \r - Carriage return (character 13) \t - Horizontal tab (character 9) \v - Vertical quote (character 11) \uxxxx - Unicode escape sequence for character with hex value xxxx \xn[n][n][n] - Unicode escape sequence for character with hex value nnnn (variable length version of \uxxxx) \Uxxxxxxxx - Unicode escape sequence for character with hex value xxxxxxxx (for generating surrogates) 

Answer 2

经过几个小时的修修补补，结果发现我一直在疯狂追逐。 问题很简单。 我从一个受欢迎的SOpost中取出了我的UPSERT 。 代码不好。 在INSERT上，select有时会返回> 1行。 从而尝试插入一行，然后再次插入相同的行 。

解决方法是删除FROM

  //UPSERT INSERT INTO [table] SELECT [col1] = @col1, [col2] = @col2, [col3] = @col3, [col4] = @col4 --FROM [table] (Dont use FROM..not a race condition, just a bad SELECT) WHERE NOT EXISTS ( SELECT 1 FROM [table] WHERE [col1] = @col1 AND [col2] = @col2 AND [col3] = @col3) UPDATE [table] SET [col4] = @col4 WHERE [col1] = @col1 AND [col2] = @col2 AND [col3] = @col3 

问题消失了。

感谢大家。

Answer 3

您正在使用'\u'生成Unicode字符。

您的列是varchar，它不支持Unicode字符。 nvarchar会支持这个角色。