postgresql - Postgres CAST macaddr

Question

假设我在 Postgres 中有两个表:

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

Name: table_mac
Column    Type
id        integer
mac       macaddr

我想做一个连接:

SELECT * FROM table_rad WHERE username = mac;

Postgres 会提示:

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.

到目前为止，我已经在谷歌上搜索了一个解决方案，我知道我必须进行 CAST。但是我怎样才能将类型 macaddr 转换为 varhcar？

Answer 1

正式风格:CAST(mac AS varchar)

PostgreSQL 风格:mac::varchar

例如:

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