Using Explicit Order By in your SQL Statements

Posted by Pramod Sadalage on Tuesday, September 30, 2008

Recently when our test databases where upgraded new version of Oracle, we started noticing that the order in which some drop down lists were being displayed was not correct. It turns out that the SELECT statement we had, did not have a ORDER BY clause and the data was being returned in the ORDER of the creation of rows (in the order of ROWID) when the database was upgraded these ROWID’s got changed and hence the ORDER of the data being shown in the drop down lists.

Lesson learnt: have a EXPLICIT ORDER BY in every SQL that provides data to be shown on the screen. In other words do not rely on the order of the result set provided by the current version of the database server. if you prefer a certain order make that choice explicit in the SQL SELECT statement.