Why use the BETWEEN operator when we can do without it?

Question

As seen below the two queries, we find that they both work well. Then I am confused why should we ever use BETWEEN because I have found that BETWEEN behaves differently in d

Answer 1

BETWEEN can help to avoid unnecessary reevaluation of the expression:

SELECT  AVG(RAND(20091225) BETWEEN 0.2 AND 0.4)
FROM    t_source;

---
0.1998

SELECT  AVG(RAND(20091225) >= 0.2 AND RAND(20091225) <= 0.4)
FROM    t_source;

---
0.3199

t_source is just a dummy table with 1,000,000 records.

Of course this can be worked around using a subquery, but in MySQL it's less efficient.

And of course, BETWEEN is more readable. It takes 3 times to use it in a query to remember the syntax forever.

In SQL Server and MySQL, LIKE against a constant with non-leading '%' is also a shorthand for a pair of >= and <:

SET SHOWPLAN_TEXT ON
GO
SELECT  *
FROM    master
WHERE   name LIKE 'string%'
GO
SET SHOWPLAN_TEXT OFF
GO


|--Index Seek(OBJECT:([test].[dbo].[master].[ix_name_desc]), SEEK:([test].[dbo].[master].[name] < 'strinH' AND [test].[dbo].[master].[name] >= 'string'),  WHERE:([test].[dbo].[master].[name] like 'string%') ORDERED FORWARD)

However, LIKE syntax is more legible.

Answer 2

Personally, I wouldn't use BETWEEN, simply because there seems no clear definition of whether it should include, or exclude, the values which serve to bound the condition, in your given example:

SELECT *
FROM emplyees
WHERE salary between 5000 AND 15000;

The range could include the 5000 and 15000, or it could exclude them.

Syntactically I think it should exclude them, since the values themselves are not between the given numbers. But my opinion is precisely that, whereas using operators such as >= is very specific. And less likely to change between databases, or between incremements/versions of the same.

---

Edited in response to Pavel and Jonathan's comments.

As noted by Pavel, ANSI SQL (http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt) as far back as 1992, mandates the end-points should be considered within the returned date and equivalent to X >= lower_bound AND X <= upper_bound:

8.3

     Function

     Specify a range comparison.

     Format

     <between predicate> ::=
          <row value constructor> [ NOT ] BETWEEN
            <row value constructor> AND <row value constructor>


     Syntax Rules

     1) The three <row value constructor>s shall be of the same degree.

     2) Let respective values be values with the same ordinal position
        in the two <row value constructor>s.

     3) The data types of the respective values of the three <row value
        constructor>s shall be comparable.

     4) Let X, Y, and Z be the first, second, and third <row value con-
        structor>s, respectively.

     5) "X NOT BETWEEN Y AND Z" is equivalent to "NOT ( X BETWEEN Y AND
        Z )".

     6) "X BETWEEN Y AND Z" is equivalent to "X>=Y AND X<=Z".

Answer 3

BETWEEN in T-SQL supports NOT operator, so you can use constructions like

WHERE salary not between 5000 AND 15000; 

In my opinion it's more clear for a human then

WHERE salary < 5000 OR salary > 15000;

And finally if you type column name just one time it gives you less chances to make a mistake

Answer 4

I'd better use the 2nd one, as you always know if it's <= or <

Answer 5

In SQL, I agree that BETWEEN is mostly unnecessary, and can be emulated syntactically with 5000 <= salary AND salary <= 15000. It is also limited; I often want to apply an inclusive lower bound and an exclusive upper bound: @start <= when AND when < @end, which you can't do with BETWEEN.

OTOH, BETWEEN is convenient if the value being tested is the result of a complex expression.

It would be nice if SQL and other languages would follows Python's lead in using proper mathematical notation: 5000 <= salary <= 15000.

One small tip that wil make your code more readable: use < and <= in preference to > and >=.