Few typical Java Developer Errors when creating SQL


Few typical Java Developer Errors when creating SQL

What is an SQL? It stands for Structured Query Language, allowing you access and manipulate databases. Moreover, it has become the ANSI or the American National Standards Institute standard back in 1986, as well as of the ISO or the International Organization for Standardization in 1987. It could execute queries against a database, insert database records, retrieve database data, and update database records, and so on.

SQL is the go-to solution for a lot of organizations all over the world, big and small. And thus, custom software development uses it to make scalable solutions. The scalability of the system is what makes it the right choice for both small and medium enterprises, and big ones as well.

An SQL server that’s configured in the right way could cut through millions of data rows. It furthermore empowers users to gain control of their data. In the custom software development service, developers could fall into several typical errors when building an SQL server.

Common Errors that Developers of Java Make when Writing an SQL Server

Always, Java developers have a rough time understanding SQL implementation. SQL is pretty straightforward, easy, and simple to write. Java, in contrast, is a complicated programming language. Developers are extremely obsessed with objects, thinking that everything has to be object-oriented.

Let’s check out some of these typical errors.

  1. Java Memory Processing of Data

SQL is well-known to only a few developers. Most developers of Java load SQL data into memory, transforming data into several appropriate types of collection, executing unpleasant math on the collection with wordy loop structures. Some SQL databases however support advanced OLAP features, which tend to do much better and considerably easier to write.

An example is the awesome MODEL clause of Oracle. Just allow the database to perform the processing and only fetch results into Java memory. By moving OLAP into the database, you acquire a couple of things:

Simplicity – writing correctly is easier in SQL than in Java

Performance – Most likely the database is faster compared to the algorithm. Most importantly, there’s no need for transmitting millions of records through the wire.

The Solution

Each time custom software developers implement a Java data-centric algorithm, they should ask themselves if there’s a way of allowing the database to do the work for them.

  1. Forgetting about NULL

Failure to understand NULL writing SQL is probably the biggest error that Java developers could make. Also, this is, but not exclusive, because NULL is otherwise called UNKNOWN. It’s easier to understand if it’s just called UNKNOWN.

One of the examples of NULL misunderstanding is when its predicates are utilized with row value expressions. Another problem that could arise but is subtler is a misunderstanding of NULL in NOT IN anti-joins.

The Solution

Consider training yourself. Think about NULL explicitly each time you write SQL. Does NULL impact the function’s result? is the predicate correct when it comes to NULL?

  1. Data Joining in Java memory

From the early SQL days, several developers have an uneasy feeling when expressions join in their SQL still. There’s a natural fear of it being slow. This could be true if a cost-based optimizer opts to do a nested loop, loading complete tables probably to the database memory, before making a joint table source. This however rarely happens.

With the right constraints, indexes, and predicates, HASH JOIN and MERGE JOIN operations are considerably fast. The correct metadata is what it all sums up to. Nevertheless, there still are probably quite several Java developers who load a couple of tables from different queries into maps, and in one way or another join them in Java memory.

The Solution

If you’re choosing from different tables in various steps, think again to determine if you couldn’t express your query in one statement.

  1. Use of UNION instead of UNION ALL

It’s unfortunate that UNION ALL requires an extra keyword than UNION. If the SQL standard has been defined in support of the following, it would be so much easier:

UNION DISTINCT – taking out duplicates

UNION – enables duplicates

Removing duplicates is not only occasionally required, and even be wrong at times, it’s also relatively slow for big sets of results with a lot of columns since the two sub-selects should be ordered and every tuple has to be compared with its subsequent tuple. Keep in mind that even an SQL standard identifies EXCEPT ALL, and INTERSECT ALL, there hardly is a database that implements these not very useful set operations.

The Solution

Each time when you write a UNION, consider if what you want or write is UNION ALL.

  1. Failure to Use the MERGE statement

This isn’t a mistake; just probably a lack of knowledge or even fear of the powerful MERGE word. Some databases know other kinds of UPSERT statements, such as instances ON DUPLICATE KEY UPDATE clause of MySQL.  However, MERGE is extremely powerful, most of all in databases that extend the SQL standard heavily, like the SQL Server.

The Solution

If you are UPSERTING through tying UPDATE and INSERT or chaining SELECT. FOR UPDATE, and inserting UPDATE or INSERTS, think again. Aside from putting at risk the race conditions, you could also express a much simpler MERGE statement.

  1. Page Large Results using JDBC Paging

A lot of databases support some method of paging ordered results via clauses including LIMIT.OFFSET, TOP. START AT, OFFSET.FETCH. In the absence of support for all these clauses, there still is a possibility of ROW NUMBER() or ROWNUM (Oracle) filtering, which is considerably faster compared to paging in memory. For big offsets, this is particularly true.

The Solution

You can simply use the clauses, or a tool like jOOQ, which could do the simulation of clauses for you.


In any custom application development service, software developers make it a point to stay updated with the latest tech trends to stay relevant. When it comes to software solutions, the SQL server makes all data available in one location. With  SQL, businesses could take advantage of financial benefits, they would become more cost-efficient and boosts their strengths as well.

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