Question

从Oracle转换为PostgreSQL，有很多SQL可以从Oracle的联接语法“（+）”转换为标准联接语法。有自动的方法-工具-来做到这一点吗？除此以外，进行此类转换时是否有经验法则？

例如，将其转换为

SELECT
    request.requestId
FROM
    request,
    incident,
    changeRequest
WHERE
    incident.requestId = request.requestId AND 
    changeRequest.requestId = request.requestId(+)
/

对此

SELECT
    request.requestId
FROM
    request
    INNER JOIN incident ON incident.requestId = request.requestId
    LEFT OUTER JOIN changeRequest ON changeRequest.requestId = request.requestId;

Answer 1

这是一种算法：

如果x.a = y.b(+)子句中有WHERE，请转动
```
FROM x, y
```
到
```
FROM x LEFT JOIN y ON x.a = y.b
```
类似于左侧的(+)和RIGHT JOIN。

有没有一种自动方法可以将Oracle的联接语法（+）转换为标准联接语法？

1 个答案: