6.2. Comparison Functions and Operators

Comparison Operators

Range Operator: BETWEEN

The BETWEEN operator tests if a value is within a specified range.It uses the syntax value BETWEEN min AND max:

SELECT 3 BETWEEN 2 AND 6;

The statement shown above is equivalent to the following statement:

SELECT 3 >= 2 AND 3 <= 6;

To test if a value does not fall within the specified rangeuse NOT BETWEEN:

SELECT 3 NOT BETWEEN 2 AND 6;

The statement shown above is equivalent to the following statement:

SELECT 3 < 2 OR 3 > 6;

The presence of NULL in a BETWEEN or NOT BETWEEN statementwill result in the statement evaluating to NULL:

SELECT NULL BETWEEN 2 AND 4; -- null
 
SELECT 2 BETWEEN NULL AND 6; -- null

The BETWEEN and NOT BETWEEN operators can also be used toevaluate string arguments:

SELECT 'Paul' BETWEEN 'John' AND 'Ringo'; -- true

Not that the value, min, and max parameters to BETWEEN and NOTBETWEEN must be the same type. For example, Presto will produce anerror if you ask it if John is between 2.3 and 35.2.

IS NULL and IS NOT NULL

The IS NULL and IS NOT NULL operators test whether a valueis null (undefined). Both operators work for all data types.

Using NULL with IS NULL evaluates to true:

select NULL IS NULL; -- true

But any other constant does not:

SELECT 3.0 IS NULL; -- false

IS DISTINCT FROM and IS NOT DISTINCT FROM

In SQL a NULL value signifies an unknown value, so any comparisoninvolving a NULL will produce NULL. The IS DISTINCT FROMand IS NOT DISTINCT FROM operators treat NULL as a known valueand both operators guarantee either a true or false outcome even inthe presence of NULL input:

SELECT NULL IS DISTINCT FROM NULL; -- false
 
SELECT NULL IS NOT DISTINCT FROM NULL; -- true

In the example shown above, a NULL value is not considereddistinct from NULL. When you are comparing values which mayinclude NULL use these operators to guarantee either a TRUE orFALSE result.

The following truth table demonstrate the handling of NULL inIS DISTINCT FROM and IS NOT DISTINCT FROM:

GREATEST and LEAST

These functions are not in the SQL standard, but are a common extension.Like most other functions in Presto, they return null if any argument isnull. Note that in some other databases, such as PostgreSQL, they onlyreturn null if all arguments are null.

The following types are supported:DOUBLE,BIGINT,VARCHAR,TIMESTAMP,TIMESTAMP WITH TIME ZONE,DATE

• greatest(value1, value2, …, valueN) → [same as input]

• Returns the largest of the provided values.

• least(value1, value2, …, valueN) → [same as input]

• Returns the smallest of the provided values.

Quantified Comparison Predicates: ALL, ANY and SOME

The ALL, ANY and SOME quantifiers can be used together with comparison operators in thefollowing way:

expression operator quantifier ( subquery )

For example:

SELECT 'hello' = ANY (VALUES 'hello', 'world'); -- true
 
SELECT 21 < ALL (VALUES 19, 20, 21); -- false
 
SELECT 42 >= SOME (SELECT 41 UNION ALL SELECT 42 UNION ALL SELECT 43); -- true

Here are the meanings of some quantifier and comparison operator combinations:

ANY and SOME have the same meaning and can be used interchangeably.