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Re: moving from MySQL to Postgres

From: Markus Bertheau <twanger(at)bluetwanger(dot)de>
To: jfabiani(at)yolo(dot)com
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: moving from MySQL to Postgres
Date: 2004-10-31 16:35:08
Message-ID: 1099240508.2695.5.camel@teetnang (view raw, whole thread or download thread mbox)
Lists: pgsql-novice
Be sure to look at information_schema for easier access to such data.

В Вск, 31.10.2004, в 17:26, John Fabiani пишет:
> Hi,
> I'm attempting to move some SQL code from a MySQL database to a Postgres 
> database.  First, I bet I'm not the only person ever to this - so I bet there 
> is a conversion white paper somewhere (if there's not - there should be). 
> Could someone point out where I might find it on the web - google didn't help 
> (most likely the wrong search string). 
> Most of the issues I have are around Metadata and how MySQL uses a simple 
> statement to produce Metadata: 
> 'SHOW tables'
> 'describe table' ....
> At the moment I'm having trouble with 'describe table' which produces three 
> columns- column name, column type, column attributes (like PK).
> The following works for the first two columns but I can't figure out how to 
> get the third column.  
> "SELECT a.attname, t.typname FROM pg_class c, pg_attribute a, pg_type t 
> WHERE c.relname = 'tablename' AND a.attnum > 0 AND a.attrelid = c.oid 
> AND a.atttypid = t.oid ORDER BY a.attnum"
> So will someone help out a novice?  I need the third column in the statement.  
> I did find I could use '-E' when starting the psql client which reproduces 
> what Postgres uses for the '\d tablename'  but it uses three statements and 
> it does not combine the index information until the end.  
> Which brings up another question.  How does the statement 2 know about the 
> results of statement 1 (same how does statement 3 know results of statement 
> 2).  Could it be that internally it created a temporary cursor?
> John
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match
Markus Bertheau <twanger(at)bluetwanger(dot)de>

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