Postgres CAST macaddr

Question

假设我在Postgres有两张桌子：

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

Name: table_mac
Column    Type
id        integer
mac       macaddr

我想加入：

SELECT * FROM table_rad WHERE username = mac;

Postgres会抱怨：

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我已经google了解决方案，我知道我必须CAST。但是如何将类型macaddr转换为varhcar？

Answer 1

正式风格：CAST(mac AS varchar)

PostgreSQL风格：mac::varchar

e.g：

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

Answer 2

您可以通过以下::text执行此操作：

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