Index Why In the DB2 : Cost Calculation 2 : index only post I noticed something upsetting, well, at least it was upsetting to me. We looked at the explain plan for looking up 1 value by an index. The index had nlevel=3. So there is a root-node, some intermediate-nodes and finally finally some leaf-nodes. …
Sometimes you need a mechanism to generate rows. For example when you need to create a demonstration table . Recursive CTE’s (Common Table Expression) might be your friend WITH engine (rownum) AS (select 1 as rownum from sysibm.sysdummy1 union all select rownum + 1 AS rownum from engine where rownum<10) SELECT rownum FROM engine; …
Every time I install a new oracle machine it hits me: Why is login.sql not executed when I start a sqlplus session. So here is a quick reminder for myself: sqlplus is not looking in $SQLPATH for login.sql ….. it is looking in $ORACLE_PATH So set $ORACLE_PATH and you will be fine. This …
Problem Playing around in DB2 I wanted to know how to create a hiearchical query. This because I wanted to create view for explain plans, a bit resembling the explain plans which oracle provides. First step is understanding how to make the recursive SQL’s The setup: drop table relations; create table relations (id int, parent …
You can have a look at v$sesstat (joined with v$staname) to see the value of some statistics at this moment. What is a little more difficult to see is how statistics change over time. So I wrote a script for it. What it does: Gather all statistics, of one or all sessions, and put them …