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Detailed explanation of the use of RLIKE operator in MySQL

藏色散人
Release: 2019-04-19 17:36:47
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In MySQL, the RLIKE operator is used to determine whether a string matches a regular expression. It is a synonym for REGEXP_LIKE().

The result is 1 if the string matches the provided regular expression, 0 otherwise.

The syntax is like this:

expr RLIKE pat
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where expr is the input string and pat is the regular expression of the test string.

Example

Here is an example of how to use this operator in a SELECT statement:

SELECT 'Tweet' REGEXP '^Tw.*t$';
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Result:

+--------------------------+
| 'Tweet' REGEXP '^Tw.*t$' |
+--------------------------+
|                        1 |
+--------------------------+
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In this case, a return value of 1 indicates that the input string matches the regular expression. In particular, we specify that the input string should start with Tw and end with t (this is because we started the pattern ^Tw and ended with t$). The . part specifies any character, and * specifies that it can be zero for any number of that (any) character. So .* means there can't be a character, one character or many characters, between start and end.

Here's what happens if we remove the *:

SELECT 'Tweet' REGEXP '^Tw.t$';
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Result:

+-------------------------+
| 'Tweet' REGEXP '^Tw.t$' |
+-------------------------+
|                       0 |
+-------------------------+
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Returning a result of 0 means no match. This is because . specifies only one instance of any character. Our input string contains two instances

SELECT 
  'Twet' REGEXP '^Tw.t$' AS 'Twet',
  'Twit' REGEXP '^Tw.t$' AS 'Twit',
  'Twt' REGEXP '^Tw.t$' AS 'Twt',
  'Tw.t' REGEXP '^Tw.t$' AS 'Tw.t';
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Result:

+------+------+-----+------+
| Twet | Twit | Twt | Tw.t |
+------+------+-----+------+
|    1 |    1 |   0 |    1 |
+------+------+-----+------+
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