How can we use sql regexp?

2 years ago
Noah Thompson
2 minutes

The REGEXP function in SQL is used to search for pattern-matching substrings within a string. Here is how it is used:

  1. The basic syntax of the REGEXP function:
  2. Retrieve the column name from the table where the column name matches the specified pattern.
  3. Pattern matching symbol:
  4. Match any character.
  5. ^: Match the beginning of the input with a specified pattern.
  6. $: matches the end of a string with a specified pattern.
  7. [ ]: specifies a set of characters to be matched. For example, [abc] will match the characters a, b, or c.
  8. [^]: Specifies a set of characters that do not match. For example, [^abc] will not match the characters a, b, or c.
  9. |: Specify one of multiple patterns for selection. For example, pattern1|pattern2 will match either pattern1 or pattern2.
  10. A combination of specified patterns.
  11. *: Match the preceding pattern zero or more times.
  12. +：Match the preceding pattern one or more times.
  13. ?: Match the preceding pattern zero or one time.
  14. {n}: Matches the preceding pattern exactly n times.
  15. {n,} : Match the previous pattern at least n times.
  16. {n,m}: Match the preceding pattern at least n times and no more than m times.
  17. Some examples:
  18. Search for lines containing a specific word:
    SELECT column_name
    FROM table_name
    WHERE column_name REGEXP ‘word’;
  19. Search for lines that start with a specific word: SELECT column_name
    FROM table_name
    WHERE column_name REGEXP ‘^word’;
  20. Find rows that end with a specific word:
    SELECT column_name
    FROM table_name
    WHERE column_name REGEXP ‘word$’;
  21. Find rows that contain a specific character set: SELECT column_name
    FROM table_name
    WHERE column_name REGEXP ‘[abc]’;
  22. Find rows that do not contain a specific set of characters: SELECT column_name
    FROM table_name
    WHERE column_name does not match the characters ‘abc’;
  23. Search for rows that contain one of multiple patterns:
    SELECT column_name
    FROM table_name
    WHERE column_name matches ‘pattern1|pattern2’;
  24. NOTE: The REGEXP function may have different syntax and functionalities in different database management systems. Please refer to the documentation of the specific database management system you are using for guidance and usage.
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