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--- postgresql [2017/06/27 09:20]
+++ postgresql [2021/04/05 11:23] (current)
@@ Line 1: / Line 1: @@
+====== 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