The MAX() function is often used to return the largest value of a given column. It's not picky about types, so the column may contain salaries, best before dates, or last names. The question is, can the MAX() function also find the highest value across multiple columns? The short answer is Yes. The longer explanation is that it depends on the database you're using. In today's blog, we'll explore a few ways to obtain the maximum value among two or more columns, either using the MAX() function, or an even better alternative.
Like most database developers, you've probably written your fair share of queries that search for that proverbial needle in a haystack of text or binary data. I know I have! Perhaps even more important than the SELECT statements that you write against the database are the indexes that it contains. To that end, an inverted index can go a long way towards making mounds of data accessible in an expeditious manner. In today's blog, we'll learn what inverted indexes are, and how to use them in your databases, using MySQL as an example.
Avoiding and/or Minimizing Deadlocks
In relational database systems (RDBMS), a deadlock is a situation where two concurrent transactions cannot make progress because each one is waiting for the other to release the lock. In Part 1 of this series, we we established what Object Locking is in Relational Databases, the different types of locks, and deadlocking. Then, in Part 2, we compared the pros and cons of Pessimistic and Optimistic locking. In this installment, we'll be exploring a few causes of deadlocks, as well as strategies for avoiding, or at least, minimizing them.
Pessimistic versus Optimistic Locking
Relational database systems (RDBMS) employ various locking strategies to enforce transaction ACID properties when modifying (e.g., UPDATING or DELETING) table records. On occasion, deadlock may occur when two concurrent transactions cannot make progress because each one is waiting for the other to release the lock. In Part 1 of this series, we we established what Object Locking is in Relational Databases, the different types of locks, and deadlocking. In today's follow-up, we'll be comparing the pros and cons of Pessimistic and Optimistic locking.
Part 1: Overview, Lock Granularity, and Deadlocks
Recently, we've had a few blogs about database transactions and they enforce the the four ACID (Atomicity Consistency Isolation Durability) properties. In today's blog, we'll be taking a look at another mechanism employed by relational databases (RDBMS) to enforce ACID properties, namely, Object Locking. Specifically, we'll learn what it is, what role(s) it plays in RDBMS transactions, and some of the side effects locking may cause. While Database Object Locking can be a fairly technical and complicated subject, we're going to break it down into layman's terms here and keep things as simple as possible.
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