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';
在本例中，年份列是带有索引的 VARCHAR2(4).
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 只是表达 inclusive 的一种简写方式i> 范围比较.当 Oracle 解析 BETWEEN 条件时，它会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
...会自动变成:
SELECT *
FROM table
WHERE :lower_bound <= column
AND :upper_bound >= column
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