normalize function

normalize converts a string to a specified Unicode normalization form.

Signatures

normalize(str)
normalize(str, form)

Return value

normalize returns a string.

Details

Unicode normalization is a process that converts different binary representations of characters to a canonical form. This is useful when comparing strings that may have been encoded differently.

The four normalization forms are:

• NFC (Normalization Form Canonical Composition): Canonical decomposition, followed by canonical composition. This is the default and most commonly used form.
• NFD (Normalization Form Canonical Decomposition): Canonical decomposition only. Characters are decomposed into their constituent parts.
• NFKC (Normalization Form Compatibility Composition): Compatibility decomposition, followed by canonical composition. This applies more aggressive transformations, converting compatibility variants to standard forms.
• NFKD (Normalization Form Compatibility Decomposition): Compatibility decomposition only.

For more information, see:

• Unicode Normalization Forms
• PostgreSQL normalize function

Examples

Normalize a string using the default NFC form:

SELECT normalize('é') AS normalized;

 normalized
------------
 é

NFC combines base character with combining marks:

SELECT normalize('é', NFC) AS nfc;

 nfc
-----
 é

NFD decomposes into base character + combining accent:

SELECT normalize('é', NFD) = E'e\u0301' AS is_decomposed;

 is_decomposed
---------------
 t

NFKC decomposes compatibility characters like ligatures:

SELECT normalize('fi', NFKC) AS decomposed;

 decomposed
------------
 fi

NFKC converts superscripts to regular characters:

SELECT normalize('x²', NFKC) AS normalized;

 normalized
------------
 x2