Articles

External Article

Automatic UNDO in Oracle

Automatic UNDO Management isn't voodoo or black magic, although it can seem that way when it isn't clearly understood. How does Oracle decide how many UNDO segments to create at startup, and what is the underlying goal of the process? David Fitzjarrell investigates.

2015-10-06

3,322 reads

External Article

Power Query Formula Language in Power BI Desktop

The Power Query Formula Language (PQFL) is a functional language that drives the Power BI transformations, and allows you to create mashup queries from scratch. In this article, Rob Sheldon demonstrates how to use it in Power BI Desktop to extract data from its source, filter rows, specify the columns, clean the data, and create visualisations.

2015-10-05

2,714 reads

SQLServerCentral Article

SQL Server Stored Procedures and SET options

SET options on stored Procedures work a bit different when compared with ad-hoc queries. These differences in behavior are often overlooked when developing the procedures and generating deployment scripts. This mistake can lead to undesired behavior in the application.

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2015-10-02 (first published: )

20,297 reads

External Article

How to Avoid Conditional JOINs in T-SQL

Relational databases go out of their way to execute SQL, however bad the crimes against Codd and relational theory within the query might be. The 'conditional join' can be executed, but at great cost. As always, it is much better to sit back and restate the problem in a set-based way - Dwain Camps explains.

2015-10-02

7,474 reads

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Question of the Day

The string_agg function

We create the following table and then insert some records in it:

create table t1 (
   id int primary key,
   category char(1) not null,
   product varchar(50)
);

insert into t1 values
(1, 'A', 'Product 1'),
(2, 'A', 'Product 2'),
(3, 'A', 'Product 3'),
(4, 'B', 'Product 4'),
(5, 'B', 'Product 5');
What happens if we execute the following query in both Sql Server and PostgreSQL?
select id, 
category, 
string_agg(product, ';')
                 over (partition by category order by id
                 rows between unbounded preceding and unbounded following) as stragg
from t1;

See possible answers