Predicates

Clojure users: note that XTDB predicates all use three-valued logic, as per the SQL spec.

The standard comparators are available:

Datalog SQL

Datalog	SQL
`(< exprs …)`	`expr1 < expr2`	less than
`(⇐ exprs …)`	`expr1 ⇐ expr2`	less than or equal to
`(> exprs …)`	`expr1 > expr2`	greater than
`(>= exprs …)`	`expr1 >= expr2`	greater than or equal to
`(= exprs …)`	`expr1 = expr2`	equal to
`(<> exprs …)`	`expr1 <> expr2`	not equal to
	`expr BETWEEN expr1 AND expr2`	shorthand for `expr1 ⇐ expr ⇐ expr2`

(< exprs …)

expr1 < expr2

less than

(⇐ exprs …)

expr1 ⇐ expr2

less than or equal to

(> exprs …)

expr1 > expr2

greater than

(>= exprs …)

expr1 >= expr2

greater than or equal to

(= exprs …)

expr1 = expr2

equal to

(<> exprs …)

expr1 <> expr2

not equal to

expr BETWEEN expr1 AND expr2

shorthand for expr1 ⇐ expr ⇐ expr2

These apply to any data types that are naturally comparable: numbers, strings, date-times, durations, etc.
If any input expression is null, the result will also be null.
The Datalog variants are variadic - they can accept any amount of arguments.
```
e.g. `(<= a b c d)` is short-hand for `(and (<= a b) (<= b c) (<= c d))`
```

Greatest / Least

These aren’t strictly predicates - they return the greatest/least value of their arguments respectively:

Datalog SQL

Datalog	SQL
`(greatest expr exprs*)`	`GREATEST(expr, …)`	returns the greatest value of the provided arguments, by the usual comparison operators
`(least expr exprs*)`	`LEAST(expr, …)`	returns the least value of the provided arguments, by the usual comparison operators

(greatest expr exprs*)

GREATEST(expr, …)

returns the greatest value of the provided arguments, by the usual comparison operators

(least expr exprs*)

LEAST(expr, …)

returns the least value of the provided arguments, by the usual comparison operators

If any provided argument is null, both of these functions will return null.

Boolean functions

Datalog SQL

Datalog	SQL
`(and exprs*)`	`expr1 AND expr2`	returns `false` if any are false, otherwise `null` if any are null, otherwise `true`
`(or exprs*)`	`expr1 OR expr2`	returns `true` if any are true, otherwise `null` if any are null, otherwise `false`
`(not expr)`	`NOT expr`	returns `true` if `expr` is false, `false` if `expr` is true, otherwise `null`
`(true? expr)`	`expr IS TRUE`	returns `true` if `expr` is true, `false` otherwise
	`expr IS NOT TRUE`	returns `false` if `expr` is true, `true` otherwise
`(false? expr)`	`expr IS FALSE`	returns `true` if `expr` is false, `true` otherwise
	`expr IS NOT FALSE`	returns `false` if `expr` is false, `true` otherwise
`(nil? expr)`	`expr IS NULL`	returns `true` if `expr` is null, `false` otherwise
	`expr IS NOT NULL`	returns `false` if `expr` is null, `true` otherwise

(and exprs*)

expr1 AND expr2

returns false if any are false, otherwise null if any are null, otherwise true

(or exprs*)

expr1 OR expr2

returns true if any are true, otherwise null if any are null, otherwise false

(not expr)

NOT expr

returns true if expr is false, false if expr is true, otherwise null

(true? expr)

expr IS TRUE

returns true if expr is true, false otherwise

expr IS NOT TRUE

returns false if expr is true, true otherwise

(false? expr)

expr IS FALSE

returns true if expr is false, true otherwise

expr IS NOT FALSE

returns false if expr is false, true otherwise

(nil? expr)

expr IS NULL

returns true if expr is null, false otherwise

expr IS NOT NULL

returns false if expr is null, true otherwise

The Datalog variants are variadic - they can accept any amount of arguments.

Numeric functions