Parsing of the CHARINDEX function usage in SQL Server (searching for characters or strings in a paragraph-----returning expression1 where the expression2 appears; Conversely, return 0)

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Knowledge Point one: CHARINDEX () syntax

        CHARINDEX ( expression1 , expression2 [ , start_location ] )解析：    expression1 必需 ---要查找的子字符串    expression2 必需 ---父字符串    start_location 可选 ---指定从父字符串开始查找的位置，默认位置从1开始

Knowledge Point two: The role of CHARINDEX ()

    从expression2字符串中指定的位置处开始查找是否包含expression1字符串

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Knowledge Point three: The return value of CHARINDEX ()

    如果能够从expression2字符串中查找到expression1字符串则返回expression1在    expression2出现的位置；反之，返回0

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Knowledge Point Four: example demonstration

1. Include:

select CHARINDEX(‘cd‘,‘abcdefg‘)

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The result is: 3

2. Does not include:

select CHARINDEX(‘dc‘,‘abcdefg‘)

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The result is: 0

Knowledge Point Four: The parameters of charindex () are case insensitive

Case:

select CHARINDEX(‘bCD‘,‘abcdefg‘)

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The result is: 2

Parsing of the CHARINDEX function usage in SQL Server (searching for characters or strings in a paragraph-----returning expression1 where the expression2 appears; Conversely, return 0)