Postgres

Config pg_hba:
local   all             postgres                                peer
local   all             postgres                                md5
local   all             all                                         md5

Cac chu de hay ve Postgres:
http://momjian.us/main/blogs/pgblog_categories.html

• One of the nicest feature of Postgresql is index on expression:http://www.postgresql.org/docs/9.0/interactive/indexes-expressional.html
  http://www.ienablemuch.com/2010/12/postgresql-speeding-up-slow-coalesce.html
• User-defined aggregates: http://developer.postgresql.org/pgdocs/postgres/xaggr.html
  http://www.ienablemuch.com/2011/02/how-to-find-second-best-grade-of_06.html
• CTE, also supports recursion http://www.ienablemuch.com/2010/04/simple-hierarchical-query-display.html
• generate_series http://www.ienablemuch.com/2010/12/date-functions.html
• Windowing functions: http://www.ienablemuch.com/2011/01/postgresql-lag-windowing-function.html
• Superb date functions http://www.ienablemuch.com/2010/12/finding-previous-day-of-week.html
• Array support: http://www.ienablemuch.com/2010/12/any-clause-is-superior-to-in-clause-at.htmlhttp://www.ienablemuch.com/2010/05/postgresql-users-are-spoiled-with.html
• Richer data types http://www.ienablemuch.com/2010/05/varchar-ip-address-sorting.html
• Functional dependency on primary keys when grouping on it (on next version, 9.1)http://www.ienablemuch.com/2010/08/postgresql-recognizing-functional.html
• User-defined operator: Adding sum of current_timestamp and days column in Postgres
• DISTINCT ON How to get the parent given a child in SQL SERVER 2005
  
  
  And don't forget the DDL, it's also transaction safe:

  BEGIN;
    ALTER TABLE foo DROP COLUMN bar;
    ALTER TABLE foo ADD COLUMN baz INET;
  COMMIT;

  Great for maintenance work, you will always have a consistent database, even when you lose the database connection or the server goes down.

Unicode:

update pg_database set datallowconn = TRUE where datname = 'template0';
\c template0
update pg_database set datistemplate = FALSE where datname = 'template1';
drop database template1;
create database template1 with template = template0 encoding = 'UTF8' LC_CTYPE = 'en_US.utf8' LC_COLLATE = 'en_US.utf8';
update pg_database set datistemplate = TRUE where datname = 'template1';
\c template1
update pg_database set datallowconn = FALSE where datname = 'template0';