Language reference
Left (leftmost characters)
Syntax
Left(<string>, <n>)
π Left(phone, 3) → area_code (Contacts)Description
Left returns the first n characters of a string. Use it to pull out prefixes — area codes, country prefixes, the first initial, a fixed-width code's leading segment.
Technical Description
Left(s: STRING, n: NUMBER) → STRING. Returns the first n characters (or the whole string if shorter). n must be non-negative (else an evaluation error). NULL string input returns NULL. PURE, DETERMINISTIC.
Examples
First three digits of a phone number:
π Left(phone, 3) → area_code (Contacts)PROJECT Left(phone, 3) -> area_code (Contacts)First initial:
π Left(first_name, 1) → initial (People)PROJECT Left(first_name, 1) -> initial (People)Pushdown
SQL: folds to LEFT(<s>, <n>) on the MySQL, PostgreSQL and DuckDB dialects, and to SUBSTR(<s>, 1, <n>) on SQLite, which lacks the name but counts the same way, and to SUBSTRING(<s>, 1, <n>, CODEUNITS32) on Db2, whose own functions count bytes unless told otherwise. Each counts a string in characters, which is what relix counts in, and each was put on that list by running it against text holding a character outside the basic multilingual plane. H2 (the generic dialect) counts UTF-16 code units, so its same-named function answers differently for such text, and is offered nothing.
Limitations
n must be ≥ 0. STRING first argument; NULL in → NULL out.
Alternatives
Right for the end of the string; Mid for a middle slice.