SQL与运算符和“> =”＆“<=”运算符之间的区别

Question

We are using a SQL query to search on the basis of dateFrom and dateTo fields. for that i am using " greater than equal to(>=) " and " less than equal to(<=) " operator to search on the date fields. somewhere i also find that we can also use SQL " Between " operator to do the same. just wanted to confirm that is there any difference when we use " Between " operator and when we used " (>= & <=) " operator.

Answer 1

There is no difference.

(x BETWEEN y AND z)

is the same as writing

((x >= y) AND (x <= z))

Answer 2

不这样没有区别（当使用ORACLE时）但使用BETWEEN运算符是比较范围值的更优雅方式。

Answer 3

Modern databases ship with very intelligent query execution optimisers. One of their main features is query transformation. Logically equivalent expressions can usually be transformed into each other. eg as Anthony suggested, the BETWEEN operator can be rewritten by Oracle (and MySQL) as two AND -connected comparisons, and vice versa, if BETWEEN isn't just implemented as syntactic sugar.

So even if there would be a difference (in performance), you can be assured that Oracle will very likely choose the better option.

This means that you can freely choose your preference, eg because of readability.

Note: it is not always obvious, what's logically equivalent. Query transformation rules become more complex when it comes to transforming EXISTS , IN , NOT EXISTS , NOT IN ... But in this case, they are. For more details read the specification (chapter 8.3 between predicate):

http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt