# Regex Reference

> Regular expression reference for StackQL: syntax, character classes, anchors, quantifiers and groups for REGEXP_LIKE, REGEXP_REPLACE and REGEXP_SUBSTR.

Source: https://stackql.io/language-spec/functions/re/reference

Reference for regular expressions used in StackQL.  

See also:  
[[` REGEXP_LIKE `]](/language-spec/functions/re/regexp_like)  [[` REGEXP_SUBSTR `]](/language-spec/functions/re/regexp_substr)  [[` REGEXP_REPLACE `]](/language-spec/functions/re/regexp_replace)

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## Supported syntax

The following regular expression syntax is supported in StackQL:    

| Expression | Description |
|------------|-------------|
| `X*` | zero or more occurrences of `X` |
| `X+` | one or more occurrences of `X` | 
| `X?` | zero or one occurrences of `X` |
| `(X)` | match `X` |
| `X`|`Y` | `X` or `Y` |
| `^X` | `X` occurring at the beginning of the string |
| `X$` | `X` occurring at the end of the string |
| `.` | Match any single character |
| `\c` | Character `c` where `c` is one of `\{}()[]`|`*+?.`
| `\c` | C-language escapes for `c` in `afnrtv`. ex: `\t` or `\n` |
| `[abc]` | Any single character from the set `abc` |
| `[^abc]` | Any single character not in the set `abc` |
| `[a-z]` | Any single character in the range `a-z` |
| `[^a-z]` | Any single character not in the range `a-z` |  

   
   
For more information, see [https://github.com/nalgeon/sqlean/blob/main/docs/re.md](https://github.com/nalgeon/sqlean/blob/main/docs/re.md)