Since version 3.2 you can use the $lookup to perform the equivalent of left outer joins in MongoDB. While you should try to design your schema to avoid joins as much as you can, the $lookup nevertheless is a very Continue reading →
On the surface, it seems like the $and operator is useless because it is implicitly applied when MongoDB processes each expression in the query. For instance the following query searches for all products where category=”vehicle” AND brand=”toyota”: However, consider this: Continue reading →
While the MongoDB Aggregation Pipeline can be used to aggregate your data, it is definitely not limited to that and can be used to construct more complicated queries that don’t necessarily do any data aggregation. One of the big advantages Continue reading →
Starting with the MongoDB Java API 3.1 a new GridFS API has been added. It is available under the com.mongodb.client.gridfs package. If you are building a new application then the new GridFS API is the recommended one to use. However Continue reading →
As a general rule, you should try to avoid joining as much as possible in MongoDB. While in traditional relational databases you try to avoid repetition of data and therefore joins are necessary, it is perfectly all right to repeat Continue reading →
Although in Linux you can easily create multi-part zip files, unzipping them can be problematic. By using the -s argument in the zip command you can specify the split size and create split archives. The following example creates split archives Continue reading →
Some time ago, Oracle removed the download links to Oracle 10g Express Edition (XE). If you need to do a new install of the Oracle XE database on your Linux platform, you can download Oracle 11g XE from the Oracle Continue reading →
When you need to schedule a Unix or Linux job in crontab to run on the first Sunday of the month, or any other weekday for that matter, your first instinct may be to write your cron entry to look Continue reading →
When I received my Geeksphone Keon last year (2013), I searched the Firefox Marketplace for a simple calculator, similar to the Calculator that comes with Windows. At the time I couldn’t find anything I liked so I wrote my own, Continue reading →
SQL Server does not natively support a “LIKE IN” clause. For instance the following example is not valid: Luckily there is a way to achieve this effect. First imagine that you have a stored procedure or function that searches for Continue reading →
