To create a gap, delete employee record from the #Employee table with id = 2 by the following script: RESULT: Now let us run the example 1’s approach 1 and 2 script on #Employee table which is having gap in the Id column value (i.e. From the above result it is clear that the example 1’s approach 1 and 2 script will not work in the scenarios where we have gap in the looping tables column values.This problem can solved in multiple ways, below are two such example approaches. Approach 1: Looping through table records where looping column has gaps in the value RESULT: Now let us run the example 2’s approach 1 and 2 script on #Employee table which is having duplicate Id column values (i.e.Quite often folks are confused about the potential of breaking relational fundamentals such as the First Normal Form or the scalar nature of typed values.(Talking about 1NF violations in a language like SQL which lacks sufficient domain support, allows NULLs and supports duplicates is somewhat ironic to begin with, but that is a topic which requires detailed explanations.) By ‘Concatenating row values’ we mean this: You have a table, view or result that looks like this……and you wish to have a resultset like the one below: In this example we are accessing the sample North Wind database and using the following SQL The objective is to return a resultset with two columns, one with the Category Identifier, and the other with a concatenated list of all the Product Names separated by a delimiting character: such as a comma.A simple, and intuitive way of displaying data is surprisingly difficult to achieve.Anith Sen gives a summary of different ways, and offers words of caution over the one you choose.This benchmark does not include very complex queries.The embedded mode of H2 is faster than the client-server mode because the per-statement overhead is greatly reduced.
I’ll take the liberty of re-posting just the first 25% or so below. The Source could also be a complete Select statement as well.
there are two records with with Id column value as 1) From the above result it is clear that the example 2’s approach 1 and 2 script will not work in the scenarios where we have duplicates in the looping column.
Here only one record of the employee with id =1 is displayed and other record is skipped.
Rather than edit that article, I’ve decided to publish a series of articles which I hope will clear up some of these misconceptions. In a nutshell, the Merge statement allows you to Insert, Update, or Delete data in an entity, referred to as the Target, with data from another entity called the Source.
If you already read the original article, a good portion of this will be review as I’m using the original as a base for this one. The entities are compared on Fields which uniquely identify records in each, a Join if you will.