RE: conditional statements

[Equ Zephyr]

I think you should be able to achieve the desired functionality in a reusable manner by writing a stored procedure / user defined function in Java as shown in the Features section of the documentation.

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From: Igal
Sent: 9/4/2012 2:55 PM
To: h2-da...@googlegroups.com
Subject: conditional statements

hi,

I'm trying to create objects only if they don't exist, but I want to use an IF-THEN statement block.  in MSSQL I would do something like:

IF NOT EXISTS( 

  SELECT  *
  FROM    INFORMATION_SCHEMA.TABLES
  WHERE   TABLE_NAME      = 'TableName'
      AND TABLE_SCHEMA    = 'public'

) BEGIN

... some sql statements here

END;

is there an equivalent H2 syntax?

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[Igal]

I considered that approach but I am working on a project that will accept different types of database engines, e.g. H2, MSSQL, MySQL, etc., so I was hoping to put the SQL code for creating objects in a single SQL script.

thanks though,

Igal

[Equ Zephyr]

I don't think there's any way you are going to be able to do that in a way that is portable across databases because it's not standard SQL. For example, it's possible to do the same thing in DB2, but the syntax is different than in MSSQL. (In DB2 it's something like "IF NOT EXISTS (...) THEN (...) ) It's also different in MySQL than it is in either MSSQL or DB2.

So really, I think this is a case where you are going to have to determine what database the user is using at runtime (possibly by checking the class name of the driver) and then use conditional logic in the Java code itself to perform the required functions.

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Date: Wed, 5 Sep 2012 11:36:08 -0700
From: ig...@getrailo.org
To: h2-da...@googlegroups.com
Subject: Re: conditional statements

To view this discussion on the web visit https://groups.google.com/d/msg/h2-database/-/bFwVuEsWRo0J.