CHARINDEX怪异

Question

您如何看待以下结果？

SELECT CHARINDEX('space and /* comment */', 'Phrase with space and /* comment */') AS MatchPosition;
DECLARE @SearchWord varchar =  'space and /* comment */'
SELECT CHARINDEX(@SearchWord, 'Phrase with space and /* comment */') AS MatchPosition;
SELECT CHARINDEX(@SearchWord, 'Phrase with space and comment') AS MatchPosition;

我期望结果1和2相同，结果3为零，但实际上结果2和3相同，并且它们也不为零，也不等于结果1。

这是怎么回事？

我没有看到这样的预防措施 https://docs.microsoft.com/en-us/sql/t-sql/functions/charindex-transact-sql?view=sql-server-2017

Answer 1

捕获在这里：

DECLARE @SearchWord varchar =  'space and /* comment */'
SELECT @SearchWord;
-- s

  

来自char and varchar

     

“当在数据定义或变量声明语句中未指定n时，默认长度为1。”

应该是：

-- defining size to avoid implicit truncating
DECLARE @SearchWord varchar(100) =  'space and /* comment */'
SELECT @SearchWord;

---

  

我期望结果1和2相同，结果3将为零

正确。

SELECT CHARINDEX('space and /* comment */', 'Phrase with space and /* comment */') AS MatchPosition;
DECLARE @SearchWord varchar(100) =  'space and /* comment */'
SELECT CHARINDEX(@SearchWord, 'Phrase with space and /* comment */') AS MatchPosition;
SELECT CHARINDEX(@SearchWord, 'Phrase with space and comment') AS MatchPosition;

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