text-manipulation functions

zhengziwei

于 2009-11-13 14:20:00 发布

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分类专栏： SQL 文章标签： string function access algorithm table sql

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本文介绍了一系列常用的文本处理函数，包括从字符串左侧或右侧获取字符、转换大小写、去除空白字符等功能，并详细解释了SOUNDEX算法，该算法可以将文本转换为描述其发音的字母数字模式。

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Commonly Used Text-Manipulation Functions
Function	Description
`LEFT()` (or use substring function)	Returns characters from left of string
`LENGTH()` (also `DATALENGTH()` or `LEN()`)	Returns the length of a string
`LOWER()`	Converts string to lowercase
`LTRIM()` (`LCASE()` if using Access)	Trims white space from left of string
`RIGHT()` (or use substring function)	Returns characters from right of string
`RTRIM()`	Trims white space from right of string
`SOUNDEX()`	Returns a string's `SOUNDEX` value
`UPPER()` (`UCASE()` if using Access)	Converts string to uppercase

One item in Table requires further explanation. SOUNDEX is an algorithm that converts any string of text into an alphanumeric pattern describing the phonetic representation of that text. SOUNDEX takes into account similar sounding characters and syllables, enabling strings to be compared by how they sound rather than how they have been typed. Although SOUNDEX is not a SQL concept, most DBMSs do offer SOUNDEX support.