Informix SQL：这种语法是什么||＆＃34; - ＆＃34; ||手段？

Question

我正在尝试了解此标志在Informix SQL中的含义＆gt;＆gt; ||"-"||

具有此问题的查询示例为：

DELETE FROM table1 WHERE field1||"-"||field2  
   IN (SELECT field1||"-"||field2 FROM table2)

Answer 1

根据评论提供的帮助，答案是 CONCATENATION ...

Answer 2

这是编写SQL的有趣方式。也许这不那么混乱，更符合标准。

DELETE FROM table1 
WHERE table1.field1 IN (SELECT table2.field1 
                        FROM table2 
                        WHERE table2.field2 = table1.field2)