PostgreSQL的10进制与16进制互转

1.10进制转16进制
Postgres里面有一个内置的10进制转16进制的函数:to_hex(int)/to_hex(bigint)

[postgres@localhost ~]$ psql
Password: 
psql (9.1.3)
Type "help" for help.

postgres=# select to_hex(9);
 to_hex 
--------
 9
(1 row)

postgres=# select to_hex(17);
 to_hex 
--------
 11
(1 row)

postgres=# select to_hex(31);
 to_hex 
--------
 1f
(1 row)

postgres=# select to_hex(255);
 to_hex 
--------
 ff
(1 row)

postgres=# select to_hex(256);
 to_hex 
--------
 100
(1 row)

2.16进制转10进制
没有内置的，参考网上的一个例子

postgres=# CREATE FUNCTION
hex_to_dec(in_hex TEXT)
RETURNS INT
IMMUTABLE STRICT LANGUAGE sql AS
$body$
  SELECT CAST(CAST(('x' || CAST($1 AS text)) AS bit(8)) AS INT);
$body$;
CREATE FUNCTION
postgres=# select hex_to_dec('1f');
 hex_to_dec 
------------
         31
(1 row)

postgres=# select hex_to_dec('ff');
 hex_to_dec 
------------
        255
(1 row)

postgres=# select hex_to_dec('fe');
 hex_to_dec 
------------
        254
(1 row)

postgres=# select hex_to_dec('09');
 hex_to_dec 
------------
          9
(1 row)

postgres=# select hex_to_dec('11');
 hex_to_dec 
------------
         17
(1 row)