Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

PostgreSQL conditions

Posted on 2000-03-21
1
1,612 Views
Last Modified: 2012-06-21
Hi!

How do I check some conditions in PostgreSQL ?!
I couldn't find any "IF" or "CASE" commands in the help.

All I want is something like that:
IF 1=1 SELECT 'True' ELSE SELECT 'False'

and more advanced:
how do I check if a table exists?
I know it's stored in pg_class table and I can check the relname field, but how can I perform something after that ?
Let's say I want to drop the table if it exists...
In Microsoft SQL server I could write somthing like that:
IF EXISTS (SELECT the table name from a system tables)
  DROP the table

How can it be done with PostgreSQL??

Thanks.
0
Comment
Question by:alex_b
1 Comment
 

Accepted Solution

by:
xbrent earned 100 total points
ID: 4380612
1>
> How do I check some conditions in PostgreSQL ?!

PostgreSQL provides for this in the form of "pl/pgsql". It is a procedural language for postgres.  See the docs (http://www.postgresql.org/users-lounge/docs/7.0/postgres/c4091.htm) for more.

IF var_i < 1 THEN
  SELECT true_column FROM table;
ELSE
  SELECT false_column FROM table;
END IF;

2>
>how do I check if a table exists..then drop?

You're correct - you check for the table using plain SQL with some plpgsql logic:

IF (SELECT tablename
      FROM pg_tables
     WHERE tablename = 'checking_for_table') ISNULL THEN
 DROP TABLE checking_for_table;
END IF;

(LANGUAGE 'plpgsql';)
0

Featured Post

Free learning courses: Active Directory Deep Dive

Get a firm grasp on your IT environment when you learn Active Directory best practices with Veeam! Watch all, or choose any amount, of this three-part webinar series to improve your skills. From the basics to virtualization and backup, we got you covered.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Entering time in Microsoft Access can be difficult. An input mask often bothers users more than helping them and won't catch all typing errors. This article shows how to create a textbox for 24-hour time input with full validation politely catching …
CCModeler offers a way to enter basic information like entities, attributes and relationships and export them as yEd or erviz diagram. It also can import existing Access or SQL Server tables with relationships.
Video by: Steve
Using examples as well as descriptions, step through each of the common simple join types, explaining differences in syntax, differences in expected outputs and showing how the queries run along with the actual outputs based upon a simple set of dem…
Polish reports in Access so they look terrific. Take yourself to another level. Equations, Back Color, Alternate Back Color. Write easy VBA Code. Tighten space to use less pages. Launch report from a menu, considering criteria only when it is filled…

828 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question