Postgres的CAST MACADDR

Question

可以說我有在Postgres的兩個表：

Name: table_rad 
Column Type 
id  integer 
username character varying(64) 

Name: table_mac 
Column Type 
id  integer 
mac  macaddr 

我想做一個加盟：

SELECT * FROM table_rad WHERE username = mac; 

Postgres將抱怨：

ERROR: operator does no exist: character varying = macaddr 
LINE 1: ...ELECT * from table_rad WHERE username = mac; 
               ^ 
Hint: No operator matches the given name and argument type(s). You might need to add explicit type casts. 

SOFAR我已經搜索了一個解決方案，我知道我必須CAST。但我怎樣才能將類型macaddr作爲varhcar？

Answer 1

正式風格：CAST(mac AS varchar)

PostgreSQL的風格：mac::varchar

如：

SELECT * FROM table_rad JOIN table_mac ON username = CAST(mac AS varchar) 

Answer 2

您可以通過::text做到像如下：

SELECT * FROM table_rad WHERE username = mac::text;