---

{ “title”: “UNICODE_NORMALIZE”, “language”: “en”, “description”: “Performs Unicode Normalization on the input string.” }

Description

Performs Unicode Normalization on the input string.

Unicode normalization is the process of converting equivalent Unicode character sequences into a unified form. For example, the character “é” can be represented by a single code point (U+00E9) or by “e” + a combining acute accent (U+0065 + U+0301). Normalization ensures that these equivalent representations are handled uniformly.

Syntax

UNICODE_NORMALIZE(<str>, <mode>)

Parameters

Parameter	Description
<str>	The input string to be normalized. Type: VARCHAR
<mode>	The normalization mode, must be a constant string (case-insensitive). Supported modes: - NFC: Canonical Decomposition, followed by Canonical Composition - NFD: Canonical Decomposition - NFKC: Compatibility Decomposition, followed by Canonical Composition - NFKD: Compatibility Decomposition - NFKC_CF: NFKC followed by Case Folding

Return Value

Returns VARCHAR type, representing the normalized result of the input string.

Examples

1. Difference between NFC and NFD (composed vs decomposed characters)

-- 'Café' where é may be in composed form, NFD will decompose it into e + combining accent
SELECT length(unicode_normalize('Café', 'NFC')) AS nfc_len, length(unicode_normalize('Café', 'NFD')) AS nfd_len;

+---------+---------+
| nfc_len | nfd_len |
+---------+---------+
|       4 |       5 |
+---------+---------+

2. NFKC_CF for case folding

SELECT unicode_normalize('ABC 123', 'nfkc_cf') AS result;

+---------+
| result  |
+---------+
| abc 123 |
+---------+

3. NFKC handling fullwidth characters (compatibility decomposition)

-- Fullwidth digits '１２３' will be converted to halfwidth '123'
SELECT unicode_normalize('１２３ＡＢＣ', 'NFKC') AS result;

+--------+
| result |
+--------+
| 123ABC |
+--------+

4. NFKD handling special symbols (compatibility decomposition)

-- ℃ (degree Celsius symbol) will be decomposed to °C
SELECT unicode_normalize('25℃', 'NFKD') AS result;

+--------+
| result |
+--------+
| 25°C   |
+--------+

5. Handling circled numbers

-- ① ② ③ circled numbers will be converted to regular digits
SELECT unicode_normalize('①②③', 'NFKC') AS result;

+--------+
| result |
+--------+
| 123    |
+--------+

6. Comparing different modes on the same string

SELECT 
    unicode_normalize('fi', 'NFC') AS nfc_result,
    unicode_normalize('fi', 'NFKC') AS nfkc_result;

+------------+-------------+
| nfc_result | nfkc_result |
+------------+-------------+
| fi          | fi          |
+------------+-------------+

7. String equality comparison scenario

-- Use normalization to compare visually identical but differently encoded strings
SELECT unicode_normalize('café', 'NFC') = unicode_normalize('café', 'NFC') AS is_equal;

+----------+
| is_equal |
+----------+
|        1 |
+----------+