Learn SQL Basics in 2019
Standard Query Language, especially going into 2019, is increasingly becoming the benchmark for manipulating and querying data in relational databases, with the caveat of having propriety extensions among the products. “NoSQL” and Hadoop, a non-relational data store, and others like them have been blown out of the water in recent times by the ease of use of SQL that they have had to at least adopt subsets of SQL or come up with SQL-like query languages of their own in order to keep up pace with SQL. This article should come in handy for any developer or anyone doing research out there and is looking to learn more about SQL.
SQL is inclusive of not only a sub-language that defines schemas but also a sub-language for modifying data, a data manipulating language (DML) and a data definition language (DDL). The first thing that we are going to look at is the SELECT statement and relational joins, a sub-language in SQL which declares queries. The SELECT statement indicates the data that should be returned, the tables to look in, the relations to follow by the optimizer as well as the order that should be imposed on the returned data. One has to be careful here so that they don’t encounter some brute force table scans, the query optimizer is basically the only thing that can prevent this as it has to decide the indexes that it will use.
When learning SQL, even at a basic level, you have to be aware of the importance of indexes especially when it comes to relational database. This is because missing indexes will lead to heavy read loads and therefore make the whole database extremely slow. On the other hand, if you have excess indexes, it will lead to heavy write and update loads which will again lead to the slowing down of the entire database. The SELECT statement needs to be used well, especially if you are looking to pull out data from a large table containing a lot of data. The syntax of how this can be done is available on runrex.com.
Another thing that is worth noting when learning the basics of SQL going into 2019 is foreign keys and the relations between tables. The presence of a primary key constraint for any table that one wants to use in relations is absolutely crucial. The primary key constraint can either take the shape of a single field or it can be a combination of fields that are defined by a given expression. The syntax of how this works can also be found on runrex.com, where you will find more meat to add to this particular bone. Something else on relational joins in SQL worth noting is the use of the CONSTRAINT keyword. This basically allows you to define and name the parameters, constraint if you will. This is important to be familiar with as it is generated by most database design tools out there nowadays.
It is also important to note when learning SQL basics in 2019 that primary keys are always indexed and are unique and therefore their field values cannot be duplicated. Indexing is however optional for the other fields and depends on preferences although as a rule of thumb, it is always advisable to create indexes for foreign key fields as well as for those keys that are in the WHERE and ORDER BY clauses. The potential overhead due to writes and updates should however dictate that this indexing should not be done every time. It is also prudent to mention that for learners of SQL basics in 2019, there are database development tools out there that can be used to generate correct SQL queries for you. This can be particularly useful since doing queries that bring together more than two tables or those that coerce data types can be quite complex given the syntax for these can be very complicated.
We should also look at SQL stored procedures as we continue with our quest to learn SQL basics in 2019. This is a provision in the database which makes use of propriety extensions that are parallel to the familiar ANSI/ISO SQL standards. This facility will sometimes prevent the SELECT statement from getting one where they want to go to. On the plus side, stored procedures are easy to use and are more efficient as they are only optimized once they are saved and not each and every time they are executed. There is a lot more to unpack on store procedures and our advice is that you check out runrex.com.
From the foregoing, SQL can get a little bit complex especially with some of the syntax involved, but learning the basics isn’t that difficult and it is something that any developer should have at least some knowledge of in 2019. Hopefully this article helps and as always there is more where that came from on runrex.com.