Top 5 Common Errors and Mistakes in SQL and How to Solve Them

After writing some SQL code, you're ready to query your database. You type in the code, and nothing happens. Instead, you're presented with an error notice.  Don't give up! SQL, like any other computer language, is prone to coding mistakes. We'll go through a few frequent mistakes individuals make while creating SQL in this tutorial.

1. Syntax error

A syntax error is the most common SQL error. What exactly does syntax imply? Essentially, it refers to a predetermined sequence of words and actions. The database will not understand what you're attempting to tell it if you utilize incorrect syntax.

Consider a spoken language to better grasp how the syntax works. Imagine saying "Nice dess" instead of "Nice dress" to someone. The individual has no idea what "dess" implies. As a result, when you instruct your database to find a TABEL instead of a TABLE, it has no idea what to do.

Because people make the same kind of syntax errors, their faults are frequently easy to identify and quite similar. You should be able to recall and avoid (or correct) these typical errors after reading this article. 

Knowing what faults to check for is crucial for new SQL developers, especially in the beginning. New programmers are more likely to make errors and spend more time looking for them.

2. Misspelling commands

This is the most common SQL error made by both new and expert developers. Let's have a peek at what it looks like. Examine the following basic SELECT query to see if you can find a flaw:

SELECT * FORM cricketer WHERE name = 'Virat';

The error we get while executing the query above is as below : 

Query Error: Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FORM cricketer WHERE name = 'Virat'' at line 1

Although the error message may be somewhat different, each database version will tell you the specific word or phrase it doesn't comprehend.

What exactly is going on here? You spelled FROM incorrectly as FORM. Misspellings in keywords (such as SELECT, FROM, and WHERE) and table and column names are widespread.

The following are the most common SQL spelling mistakes:

• When you strike a letter near the right one, you get "chubby fingers": WJIRE, FTOM, or SELEVT
• When you enter the proper letters in the wrong sequence, it's known as "reckless typing": SELETC, FORM, or WHEER are all terms for the same thing.

Solution:

If you use a SQL editor with syntax highlighting, the SELECT and WHERE keywords will be highlighted, but the misspelled FORM will not.

3. Forgetting brackets and quotes

Brackets combine actions together and direct the sequence in which they are carried out. The order of operations in SQL (and all of the computer languages I use) is different.

SELECT * FROM cricketer 
WHERE franchise = 'rcb' and (name = 'Virat' or name = 'Jadeja');


SELECT * FROM cricketer 
WHERE franchise = 'rcb' and name = 'Virat' or name = 'Jadeja';

Both the queries produce similar results but note that they are not the same queries. They are different. We have used our old database from previous articles.

Can you guys figure out the error in the below query?

SELECT * FROM cricketer 
WHERE franchise = 'rcb' and (name = 'Virat' or name = 'Jadeja';

Query Error: Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 2

Single quotes (' ') and double quotes (" ") work in the same way. In SQL, we can never discover a quotation (either a single or double quote) without its mate.

Solution

It's all about practice, practice, practice. More SQL code will provide you with the experience you'll need to prevent these blunders. Also, keep in mind that most individuals overlook the closing bracket or quote mark. They almost never leave out the first one. Take a hard look at all of your ending punctuation if you're having trouble.

4. Invalid statement order

When constructing SELECT statements, keep in mind that the statement must be written in a specific order in order to run correctly. There is no room for error here.

Consider the following example of a properly-ordered statement:

SELECT name
FROM cricketer
WHERE name = 'Virat'
GROUP BY name
HAVING count(*) = 1
ORDER BY name;

There is no shortcut here; you just need to remember the SELECT statement's exact keyword order:

• SELECT returns a list of column names and functions.
• If you're utilizing several tables, FROM gives the table name or names (as well as JOIN requirements).
• WHERE Filtering statements are defined.
• GROUP BY demonstrates how to categorize columns.
• THE GROUPED VALUES HAVE BEEN FILTERED
• ORDER BY determines the display order of the results.

Can you guys figure out the issue below query??

SELECT name
FROM cricketer
WHERE name = 'Virat'
GROUP BY name 
ORDER BY name
HAVING count(*) = 1;

Query Error: Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'HAVING count(*) = 1' at line 6

Solution

Don't let yourself down! All of the keywords are appropriately highlighted, and all quotes and brackets are closed, as you can see. As a result, you should now double-check the statement order. I recommend employing a SELECT order checklist while you're first learning SQL. If you have an issue, look up the right order on your list.

Conclusion

These are the most frequent SQL code mistakes. As you master this language, you'll most likely make them several times. Remember that everyone makes mistakes when it comes to developing code. Making errors is, in fact, an unavoidable component of software development.

Don't let this discourage you. In the future, if you make a mistake, attempt to evaluate your code in a methodical manner. You can detect and repair issues faster with systematic analysis.