Becoming an SQL master is an ambition that many people foster, but unless you take the right route, you might have a harder time achieving it than is really necessary.
Here are just 6 steps which should hopefully provide a framework to take you from an eager beginner to a more experienced SQL user without ever feeling like you are hitting a wall.
Suboptimal queries hurt performance
Writing efficient queries is central to taking the reins in any SQL role, and a quick look at SQL server wait stats will show you if you are running into any bottlenecks that need to be dealt with.
Thankfully you can counteract performance bottlenecks without needing to upgrade server hardware by simply writing queries in an optimal way. Rather adding extra processing time to each request because you have added the DISTINCT clause to the SELECT statement, for example, it is generally less intensive and thus faster to leave this out if possible.
Another way to streamline results is to impose more specific requirements on them as part of the SELECT statement.
You can set a predetermined cap by using the LIMIT clause, if you wish, or take a less rigid but no less useful approach by using PERCENT to filter results.
Simplicity is your friend
Once you feel like you are getting pretty familiar with SQL syntax, you may be tempted to start throwing in more clauses and operators that you have learned about in your tinkering. For example, the SQL NOT LIKE and LIKE operators, used to filter data.
In reality, simple is often better than complex, so do not be afraid to stick with more basic queries, because there is no shame in being economical with your inputs; just ask SQL veterans.
Query plans can pinpoint problems
The management system you use to wrangle your SQL database should be able to provide you with a query plan which maps out queries and makes them easier to scrutinize, digest and tweak as necessary.
Query plans which are represented graphically, rather than purely in text, can be particularly empowering as they make it easier to visualize the process you are working on, so leverage this tool to your advantage if possible.
Index scanning saves time
In the case that you are working with an especially large dataset, it makes less sense to carry out a table scan when an index scan will usually get you the results you need faster.
This is achieved because instead of scouring an entire table, the query engine will instead look only within a given index, only moving on to search elsewhere if it comes up empty handed. Of course in the case that your database is of a more modest size, a table scan could potentially be more efficient.
Security is crucial
While you are developing your skills with SQL, do not forget that database security is just as important as efficiency and performance.
SQL injection is still a popular hacking tactic and so learning to prevent this to protect private information is all part of mastering SQL.
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