LOCATE and POSITION of string functions intercepted by MySQL

We know that mysql does not include charindex function truncation characters like mssql, but mysql seems to provide more character truncation functions than mssql, next I will introduce to you the usage of the mysql character truncation function.

MySQL string truncation functions: left (), right (), substring (), substring_index (). There are also mid () and substr (). Here, mid () and substr () are equivalent to substring ().

LOCATE (substr, str)
POSITION (substr IN str)

Returns the position of the substring substr that appears for the first time in the str string. If the substring substr does not exist in str, the return value is 0:

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Mysql> select locate ('bar', 'foobarbar '); -> 4 Mysql> select locate ('xbar', 'foobar '); -> 0

This function is multi-byte secure. In MySQL 3.23, this function is case-sensitive. in MySQL 4.0, if any parameter is a binary string, it is case-sensitive.

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LOCATE (substr, str, pos)

Returns the position where the substring substr first appears after the position pos in the str string. If substr is not in str, return 0:

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Mysql> select locate ('bar', 'foobarbarbar ', 5 ); -> 7

This function is multi-byte secure. In MySQL 3.23, this function is case-sensitive. in MySQL 4.0, if any parameter is a binary string, it is case-sensitive.

Example:

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Select info. * from info left join attribute as a on POSITION (CONCAT (substr ('20140901', 00000-LENGTH (info. fid), info. fid) IN. fid) <> 0

 

Other methods for intercepting characters

1. Extract strings from the left
Left (str, length)

Note: left (truncated field, truncated length)
Example:

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Select left (content, 200) as abstract from my_content_t

2. Extract strings from the right
Right (str, length)

Note: right (intercepted field, truncated length)
Example:

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Select right (content, 200) as abstract from my_content_t

3. truncate a string
Substring (str, pos)
Substring (str, pos, length)

Description: substring (truncated field, starting from the nth digit)
Substring (truncated field, starting from the nth digit and intercepting the length)
Example:

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Select substring (content, 5) as abstract from my_content_t Select substring (content, 5,200) as abstract from my_content_t

(Note: if the number of digits is negative, for example,-5, it is the length from the last to the end or truncation of the string)

4. truncate a string by keyword
Substring_index (str, delim, count)

Note: substring_index (intercepted field, keyword, number of times the keyword appears)
Example:

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Select substring_index ("blog.chinabyte.com", ".", 2) as abstract from my_content_t