How to use regular expressions in sql

Regular expressions used in SQL can be used to match strings using POSIX syntax through the REGEXP_LIKE() function. Commonly used characters include anchor characters, character classes, and quantifiers. Regular expressions can be used to search and extract data in SELECT, WHERE, and other statements, but different database systems have slightly different support for regular expressions.

How to use regular expressions in SQL

Introduction to regular expressions
Regular expression (Regex) is a series of character patterns used to match strings that meet specific rules. In SQL, regular expressions can be used to search and extract data within strings.

Using regular expressions in SQL
The syntax for using regular expressions in SQL is:

<code>REGEXP_LIKE(string_to_search, regex_pattern)</code>

Among them:

• string_to_search: The string to search for.
• regex_pattern: Regular expression pattern to match.

POSIX Regular Expressions
SQL uses POSIX regular expression syntax. Commonly used POSIX regular expression characters include:

• Anchor character:

  • ^: string Starting position
  • $: String ending position

• Character class:

  • []: Matches a character within square brackets
  • [a-z]: Matches lowercase letters
  • [0- 9]: Matches the number

• Quantifier:

  • *: Matches 0 or more
  • : Match 1 or more times
  • ?: Match 0 or 1 time

Example

• Matches strings starting with "abc":

  <code>REGEXP_LIKE('abcabc', '^abc')</code>

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• Matches strings containing "cc":

  <code>REGEXP_LIKE('acccb', '(cc)')</code>

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• Matches strings ending with numbers:

  <code>REGEXP_LIKE('123456', '$[0-9]')</code>

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Note:

• Characters in regular expressions are case-sensitive.
• Regular expressions can be used in SELECT, WHERE and other SQL statements.
• Different database systems may have slightly different support for regular expressions.

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