Language reference
CONCAT (join values as text, skipping NULLs)
Syntax
CONCAT(<value>, <value>, ...)
π CONCAT(first_name, ' ', name) → full (Users)Description
CONCAT joins any number of values into one string, in order. A missing value adds nothing rather than making the whole result missing, which is where it differs from + and ||: CONCAT('a', NULL, 'b') is 'ab', where 'a' + NULL + 'b' is NULL. A number or a date is written as it displays.
Technical Description
CONCAT(value, …) → STRING. One or more arguments of any type; each non-NULL argument contributes its display text, and NULLs contribute nothing, so the result is never NULL. This is PostgreSQL's and SQL Server's CONCAT; MySQL's returns NULL when any argument is NULL. PURE, DETERMINISTIC.
Examples
A label from a number and text:
π CONCAT('#', order_id, ' ', status) → label (Orders)PROJECT CONCAT('#', order_id, ' ', status) -> label (Orders)A full name that survives a missing first name:
π CONCAT(first_name, ' ', name) → full (Users)PROJECT CONCAT(first_name, ' ', name) -> full (Users)Pushdown
Runs in the engine: a backend writes numbers and dates as text in its own way.
Alternatives
+ or || between two strings, which is NULL when either is.