BETWEEN子句与< = AND> = [英] BETWEEN clause versus <= AND >=
本文介绍了BETWEEN子句与< = AND> =的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
使用BETWEEN子句或使用< = AND> =比较之间是否存在性能差异?
Is there a performance difference between using a BETWEEN clause or using <= AND >= comparisons?
即这两个查询:
SELECT *
FROM table
WHERE year BETWEEN '2005' AND '2010';
...和
SELECT *
FROM table
WHERE year >= '2005' AND year <= '2010';
在此示例中,年份列是VARCHAR2(4),上面有一个索引.
In this example, the year column is VARCHAR2(4) with an index on it.
推荐答案
两个示例查询之间没有性能差异,因为BETWEEN
只是表示包含范围范围比较的简写方式.当Oracle解析BETWEEN
条件时,它将自动扩展为单独的比较子句:
There is no performance difference between the two example queries because BETWEEN
is simply a shorthand way of expressing an inclusive range comparison. When Oracle parses the BETWEEN
condition it will automatically expand out into separate comparison clauses:
例如.
SELECT *
FROM table
WHERE column BETWEEN :lower_bound AND :upper_bound
...将自动变为:
SELECT *
FROM table
WHERE :lower_bound <= column
AND :upper_bound >= column
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