Language reference
CBool (convert to boolean)
Syntax
CBool(<value>)
π id, CBool(active_flag) → active (Imports)Description
CBool reads a value as TRUE or FALSE: a number is TRUE unless it is zero, and text is one of the words SQL uses for the two, such as yes, no, true, false, 1 and 0. Use it to turn flags imported as text or numbers into booleans you can test. CAST(x AS BOOLEAN) is CBool with a NULL passed through.
Technical Description
CBool(value) → BOOLEAN. A BOOLEAN is itself; a NUMBER is FALSE for zero and TRUE otherwise; a STRING, trimmed and in any letter case, is TRUE for t, true, y, yes, on and 1 and FALSE for f, false, n, no, off and 0, as PostgreSQL reads them. Any other text is an evaluation error naming it, as are NULL, a date or time and a nested value. PURE, DETERMINISTIC.
Examples
A flag imported as text:
σ CBool(subscribed) = TRUE (Imports)SELECT CBool(subscribed) = TRUE (Imports)A count read as "any at all":
π id, CBool(open_tickets) → has_open (Accounts)PROJECT id, CBool(open_tickets) -> has_open (Accounts)Limitations
NULL is an error, as it is for CStr, CInt and CDbl; CAST(x AS BOOLEAN) returns NULL for it instead.
Alternatives
A comparison, open_tickets > 0, says the same as CBool of a count, and IsNumeric asks whether text holds a number.