hstore:不能连接两个hstore值

Question

Postgres的新手使用v9.3，希望利用hstore。

当我试图连接两个hstore值时，会得到一个奇怪的错误：

SELECT p.properties->'name' || p.properties->'age' FROM people p where p.id=1;

错误是：

ERROR:  operator does not exist: text -> unknown
LINE 1: select n.properties->'name' || n.properties->'age' from n...
                                                   ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.

我也试过了，这不重要：

SELECT p.properties->'name'::text || p.properties->'age'::text FROM people p where p.id=1;

不过，我可以

SELECT p.properties->'name' FROM people p where p.id=1;

SELECT p.properties->'age' FROM people p where p.id=1;

难道不可能在同一个hstore中连接两个hstore值吗？

任何指导者都会感激的！

Answer 1

您可以按照如下方式处理强制转换函数：

SELECT CAST(p.properties->'name' AS text) || CAST(p.properties->'age' AS text) FROM people p where p.id=1;