PSQL：字符串连接和输出字符串

Question

我是 psql 的新手。 我有一张“宠物”桌，如下所示。

    name     | species |       owner        | gender |     color
-------------+---------+--------------------+--------+---------------
 Nagini      | snake   | Lord Voldemort     | female | green
 Hedwig      | owl     | Harry Potter       | female | snow white
 Scabbers    | rat     | Ron Weasley        | male   | unspecified
 Pigwidgeon  | owl     | Ron Weasley        | male   | grey
 Crookshanks | cat     | Herminone Granger  | male   | ginger
 Mrs Norris  | cat     | Argus Filch        | female | dust-coloured
 Trevor      | toad    | Neville Longbottom | male   | brown

如何连接字符串并以给出“Ron Weasley 有 X 个宠物”（其中 X = 2）的方式输出字符串？

我知道 X=2 部分的 'select count(name) from pets where owner = 'Ron Weasley';'，但不确定如何在 PSQL 中连接和输出字符串。

Answer 1

SELECT p.owner||' has ' count(p.name)||' pets' as conc_output
  FROM pets p
 WHERE owner = 'Ron Weasley';