Oracle中的显式游标和隐式游标有什么区别? [英] What is the difference between explicit and implicit cursors in Oracle?

问题描述

我对PL/SQL中的游标行话有点生疏.有人知道吗?

I am a bit rusty on my cursor lingo in PL/SQL. Anyone know this?

推荐答案

隐式游标是Oracle在执行查询时为您自动"创建的一个游标.它更易于编码，但会受到

An implicit cursor is one created "automatically" for you by Oracle when you execute a query. It is simpler to code, but suffers from

• 效率低下(ANSI标准规定必须提取两次才能检查是否有多条记录)
• 易受数据错误影响(如果您遇到两行，则会引发TOO_MANY_ROWS异常)

示例

SELECT col INTO var FROM table WHERE something;

显式游标是您自己创建的游标.它需要更多的代码，但是却提供了更多的控制权-例如，如果您只想要第一条记录而不必关心是否还有其他记录，则可以只打开-获取-关闭.

An explicit cursor is one you create yourself. It takes more code, but gives more control - for example, you can just open-fetch-close if you only want the first record and don't care if there are others.

示例

DECLARE   
  CURSOR cur IS SELECT col FROM table WHERE something; 
BEGIN
  OPEN cur;
  FETCH cur INTO var;
  CLOSE cur;
END;

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