====== PostgreSQL ======

===== Row Id =====
Each table has a column CTID which holds the row id of a row.

  SELECT ctid FROM mytable;


===== Current Transactions =====

  SELECT datname,usename,procpid,client_addr,waiting,query_start,current_query FROM pg_stat_activity;
  
===== Exception Join =====
The exception join can be created with the combination of the left outer join and the query on null.

Table a:
  * id
  * name

Table b:
  * pid
  * fid
  * longitude
  * latitude

Select every entry from table a which has no entry in table b.

<sxh sql>
  SELECT *
  FROM a LEFT OUTER JOIN b ON (a.id = b.fid)
  WHERE b.pid IS NULL
</sxh>

===== Table Scan Options =====

  set enable_seqscan=true;
  set enable_indexscan=true;

===== Command Line Client =====

==== Show Tables ====

  \d
  
==== Show Columns ====

  \d table_name
  
==== Show Databases ====
  
  \l