INPUT:

-- Postgresql 7.4.0
-- ##########################################################
DROP TABLE chartest; -- may give error (OK)
CREATE TABLE chartest (
  charval1 CHAR(10) NOT NULL,
  charval2 CHAR(10) NOT NULL,
  varcharval VARCHAR(30) NOT NULL
);
INSERT INTO chartest VALUES ('aaa','aaa','aaa');
INSERT INTO chartest
  VALUES ('aaaaaaaaaaaa','aaa','aaa'); -- should give error
SELECT * FROM chartest;
SELECT * FROM chartest WHERE charval1=varcharval;
SELECT charval1 || 'X' AS res FROM chartest;
SELECT CHAR_LENGTH(charval1 || charval2) AS res FROM chartest;
SELECT character_length(charval1) + character_length(charval2)
  AS res
  FROM chartest;



OUTPUT:

test=> -- Postgresql 7.4.0
test=> -- ##########################################################
test=> DROP TABLE chartest; -- may give error (OK)
DROP TABLE
test=> CREATE TABLE chartest (
test(>   charval1 CHAR(10) NOT NULL,
test(>   charval2 CHAR(10) NOT NULL,
test(>   varcharval VARCHAR(30) NOT NULL
test(> );
CREATE TABLE
test=> INSERT INTO chartest VALUES ('aaa','aaa','aaa');
INSERT 24536 1
test=> INSERT INTO chartest
test->   VALUES ('aaaaaaaaaaaa','aaa','aaa'); -- should give error
ERROR:  value too long for type character(10)
test=> SELECT * FROM chartest;
  charval1  |  charval2  | varcharval
------------+------------+------------
 aaa        | aaa        | aaa
(1 row)
 
test=> SELECT * FROM chartest WHERE charval1=varcharval;
  charval1  |  charval2  | varcharval
------------+------------+------------
 aaa        | aaa        | aaa
(1 row)
 
test=> SELECT charval1 || 'X' AS res FROM chartest;
 res
------
 aaaX
(1 row)
 
test=> SELECT CHAR_LENGTH(charval1 || charval2) AS res FROM chartest;
 res
-----
   6
(1 row)
 
test=> SELECT character_length(charval1) + character_length(charval2)
test->   AS res
test->   FROM chartest;
 res
-----
  20
(1 row)