Oracle SQL-连接语法/关键字 [英] Oracle SQL - Joins Syntax/Keywords

问题描述

查询Oracle数据库时:

When querying an Oracle DB:

如果查询是带有联接的选择，语法是否必须包含关键字:

If the query is a select with joins, does the syntax have to include the keywords:

• 内部加入
• 外加入
• 左/右外联接

如果不是，那么替代用法/语法是什么?

If not, then what are the alternative usages/syntax?

之所以这样问，是因为我正在查看一个SELECT语句，该语句在FROM子句中不使用任何JOIN关键字，但是在WHERE子句中包含连接语法，我想知道:

I ask this because I am looking at a SELECT statement that does not use any of the JOIN keywords within the FROM clause, but includes the joining syntax within the WHERE clause, and I am wondering:

• 如果所选内容正在执行JOIN
• 如果是，查询的是哪种JOIN ?

• if the select is executing a JOIN
• if so, what kind of JOIN is it querying?

示例:

SELECT e.name, e.employeeid, d.sales, d.task, sum(d.hours)
FROM employee e,
       timecard d,
WHERE e.employeeid = d.employeeid and
GROUP BY ...
ORDER BY ...

推荐答案

是的，这是(内部)联接，可以重写为

Yes, this is a (inner) join, and could be rewritten as

SELECT e.name, e.employeeid, d.sales, d.task, sum(d.hours)
FROM employee e
JOIN timecard d on e.employeeid = d.employeeid
WHERE ...
GROUP BY ...
ORDER BY ...

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