---
title: "Text basics"
slug: "dev-database-reference-sql-functions-string-text-basics"
updated: 2026-10-30T18:18:56Z
published: 2026-10-30T18:18:56Z
canonical: "docs.vastdata.com/dev-database-reference-sql-functions-string-text-basics"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Text basics

*Applies to VAST Cluster 5.5.*

Length, case, concatenation, parts of a string, replacing, code points, formatting, Unicode and URLs, string similarity and file paths.

Each function has its own page: syntax, what it does, NULLs and edge cases, examples with their output, how it runs in VAST, how to make it faster, limitations and errors, and similar functions. Names that the VAST Query Engine doesn't have are in [all functions A-Z](/develop/docs/dev-database-reference-sql-functions-a-z).

## Characters and code points

| Function | What it does |
| --- | --- |
| [ascii](/develop/docs/dev-database-reference-sql-functions-string-ascii) | Return the Unicode code point of the first character of a VARCHAR, including code points above 127. |
| [chr](/develop/docs/dev-database-reference-sql-functions-string-chr) | Return the character with a given Unicode code point as a VARCHAR, and the errors for numbers that aren't valid code points. |
| [ord](/develop/docs/dev-database-reference-sql-functions-string-ord) (also `unicode`) | Return the Unicode code point of the first character of a VARCHAR, or -1 for an empty string; unicode is the same function. |

## Length

| Function | What it does |
| --- | --- |
| [bit_length](/develop/docs/dev-database-reference-sql-functions-string-bit-length) | Count the bits in the UTF-8 encoding of a VARCHAR, or the bits of a BIT value. |
| [length_grapheme](/develop/docs/dev-database-reference-sql-functions-string-length-grapheme) | Count the grapheme clusters in a VARCHAR, what a reader sees as characters. |
| [length](/develop/docs/dev-database-reference-sql-functions-string-length) (also `len`) | Count the characters in a VARCHAR, the bits in a BIT value or the elements of a list; len is the same function. |
| [strlen](/develop/docs/dev-database-reference-sql-functions-string-strlen) | Count the bytes in the UTF-8 encoding of a VARCHAR. |

## Case

| Function | What it does |
| --- | --- |
| [COLLATE nocase and noaccent](/develop/docs/dev-database-reference-sql-functions-string-collate) | Compare strings without regard to case, accents or both with COLLATE nocase, noaccent and nocase.noaccent. |
| [lower](/develop/docs/dev-database-reference-sql-functions-string-lower) (also `lcase`) | Convert a VARCHAR to lower case, including letters outside ASCII; lcase is the same function. |
| [upper](/develop/docs/dev-database-reference-sql-functions-string-upper) (also `ucase`) | Convert a VARCHAR to upper case, including letters outside ASCII; ucase is the same function. |

## Concatenation

| Function | What it does |
| --- | --- |
| [\|\| (concatenation)](/develop/docs/dev-database-reference-sql-functions-string-concat-operator) | Join two strings, two lists or two BLOB values with the \|\| operator; a NULL on either side gives NULL. |
| [concat_ws](/develop/docs/dev-database-reference-sql-functions-string-concat-ws) | Join values into one VARCHAR with a separator between them, skipping NULL values. |
| [concat](/develop/docs/dev-database-reference-sql-functions-string-concat) | Join values into one string, skipping NULLs, or join lists. |

## Similarity

| Function | What it does |
| --- | --- |
| [damerau_levenshtein](/develop/docs/dev-database-reference-sql-functions-string-damerau-levenshtein) | Return the edit distance between two strings, counting a swap of two neighbouring characters as one edit. |
| [hamming](/develop/docs/dev-database-reference-sql-functions-string-hamming) (also `mismatches`) | Count the positions at which two strings of the same length differ; mismatches is the same function. |
| [jaccard](/develop/docs/dev-database-reference-sql-functions-string-jaccard) | Return the Jaccard similarity of the sets of characters in two strings, from 0 to 1. |
| [jaro_similarity](/develop/docs/dev-database-reference-sql-functions-string-jaro-similarity) | Score how alike two strings are, from 0.0 to 1.0, with the Jaro similarity, optionally with a cutoff below which the score is 0.0. |
| [jaro_winkler_similarity](/develop/docs/dev-database-reference-sql-functions-string-jaro-winkler-similarity) | Score how alike two strings are with the Jaro-Winkler similarity: the Jaro score, raised for strings that start the same way, with an optional cutoff. |
| [levenshtein](/develop/docs/dev-database-reference-sql-functions-string-levenshtein) (also `editdist3`) | Return the edit distance between two strings: the fewest insertions, deletions and substitutions that turn one into the other; editdist3 is the same function. |

## Formatting

| Function | What it does |
| --- | --- |
| [format](/develop/docs/dev-database-reference-sql-functions-string-format) | Build a VARCHAR from a template with {} placeholders, positions and format specifications for width, alignment, decimals and number bases. |
| [printf](/develop/docs/dev-database-reference-sql-functions-string-printf) | Build a VARCHAR from a C-style template with %s, %d, %f, %x and other conversions, widths and precisions. |

## Parts of a string

| Function | What it does |
| --- | --- |
| [left_grapheme](/develop/docs/dev-database-reference-sql-functions-string-left-grapheme) | Return the first n grapheme clusters of a VARCHAR, so accented letters and flag emoji are never cut in half. |
| [left](/develop/docs/dev-database-reference-sql-functions-string-left) | Return the first n characters of a VARCHAR, or all but the last n with a negative count. |
| [right_grapheme](/develop/docs/dev-database-reference-sql-functions-string-right-grapheme) | Return the last n grapheme clusters of a VARCHAR, so accented letters and flag emoji are never cut in half. |
| [right](/develop/docs/dev-database-reference-sql-functions-string-right) | Return the last n characters of a VARCHAR, or all but the first n with a negative count. |
| [substring_grapheme](/develop/docs/dev-database-reference-sql-functions-string-substring-grapheme) | Return part of a VARCHAR by start position and length, counted in grapheme clusters, so accented letters and flag emoji are never cut in half. |
| [substring](/develop/docs/dev-database-reference-sql-functions-string-substring) (also `substr`, `SUBSTRING(s FROM start FOR length)`, `substring(s, start, length)`) | Return part of a VARCHAR by start position and length; substr, SUBSTRING(s FROM a FOR b) and the s[start:end] and s[i] slices do the same. |

## Unicode and URLs

| Function | What it does |
| --- | --- |
| [nfc_normalize](/develop/docs/dev-database-reference-sql-functions-string-nfc-normalize) | Convert a string to Unicode normalization form C, so a letter and a combining accent become one character and equal-looking text compares equal. |
| [strip_accents](/develop/docs/dev-database-reference-sql-functions-string-strip-accents) | Remove accents from the letters of a string, for accent-insensitive search and matching. |
| [url_decode](/develop/docs/dev-database-reference-sql-functions-string-url-decode) | Decode a percent-encoded URL string: each % and two hexadecimal digits becomes the byte it stands for. |
| [url_encode](/develop/docs/dev-database-reference-sql-functions-string-url-encode) | Percent-encode a string for use in a URL: every byte other than letters, digits and - . _ ~ becomes % and two hexadecimal digits. |

## Paths

| Function | What it does |
| --- | --- |
| [parse_dirname](/develop/docs/dev-database-reference-sql-functions-string-parse-dirname) | Get the top-level directory of a file path: the first component, or / for an absolute path. |
| [parse_dirpath](/develop/docs/dev-database-reference-sql-functions-string-parse-dirpath) | Get the directory part of a file path: everything before the last separator. |
| [parse_filename](/develop/docs/dev-database-reference-sql-functions-string-parse-filename) | Get the file name at the end of a path, optionally without its last extension and with a chosen separator. |
| [parse_path](/develop/docs/dev-database-reference-sql-functions-string-parse-path) | Split a file path into a list of its components, splitting on / and \ by default or on one separator you choose. |

## Changing text

| Function | What it does |
| --- | --- |
| [repeat](/develop/docs/dev-database-reference-sql-functions-string-repeat) | Repeat a VARCHAR, a BLOB or a list a number of times. |
| [replace](/develop/docs/dev-database-reference-sql-functions-string-replace) | Replace every occurrence of a substring in a VARCHAR with another string, without patterns. |
| [reverse](/develop/docs/dev-database-reference-sql-functions-string-reverse) | Reverse the characters of a VARCHAR, keeping accented letters and flag emoji whole. |
| [translate](/develop/docs/dev-database-reference-sql-functions-string-translate) | Replace or remove single characters of a VARCHAR, each by the character at the same position in a second string. |

## See also

- [SQL functions](/develop/docs/dev-database-reference-sql-functions-index) and [all functions A-Z](/develop/docs/dev-database-reference-sql-functions-a-z).