什么是@!在From语句中表示

Question

我想确定一下这个代码做什么(甲骨文SQL) -尤其是在签收感叹号中from的条款.

INSERT INTO "LOCATIONS" "A1"
            ("LOCATION_ID",
             "SEQUENCE",
             "POINT_TYPE")
SELECT "A2"."LOCATION_ID",
       "A2"."SEQUENCE",
       "A2"."LOCATION_TYPE",
       "A2"."POINT_TYPE"
FROM   "LOCATIONS"@! "A2"
WHERE  NOT EXISTS (SELECT 1
                   FROM   "LOCATIONS" "A3"
                   WHERE  "A3"."LOCATION_ID" = "A2"."LOCATION_ID") 

Answer 1

这是指向执行查询的原始数据库的反向数据库链接.原始查询必须如下所示:

INSERT INTO LOCATIONS@remote_db
            ("LOCATION_ID",
             "SEQUENCE",
             "POINT_TYPE")
SELECT "A2"."LOCATION_ID",
       "A2"."SEQUENCE",
       "A2"."POINT_TYPE"
FROM   "LOCATIONS" A2
WHERE  NOT EXISTS (SELECT 1
                   FROM   LOCATIONS@remote_db A3
                   WHERE  "A3"."LOCATION_ID" = "A2"."LOCATION_ID");

这样,所有远程表都变为本地,本地表变为远程表"@!".

Answer 2

我认为这不是有效的 SQL。检查您的代码以确保在执行 SQL 之前没有任何更改 - 特别是检查数据库链接的名称是否被替换为!.

如果您无法确定正在执行什么，您可以在数据库上进行跟踪