intro
How do you know if two values are equal? You can use the equality operator – or you can use the NULLIF function – here’s everything you need to know.
MySQL and other database management systems have many functions. Each of those functions solve a concrete problem NULLIF, or IFNULL, is used to figure out whether two values are equal. In other words, both NULLIF or MySQL IFNULL (these functions mean one and the same) returns a specified value if an expression is NULL, and otherwise, returns the expression specified by the user.
Flow Control Functions in MySQL
MySQL defines IFNULL as one of the flow control functions available in the DBMS. MySQL has different flow control functions, including:
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SELECT ... CASE WHEN [condition] THEN [outcome] [ELSE other result] END
Such a query returns a string if an ID is less, equal, or more than 2, and such queries are used to return a string or a value once a specific condition is met.
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SELECT IFNULL(“Basic”, “DbVisualizer”);
Such a query would, of course, return the string “Basic”, because the expression isn’t NULL:
All flow control functions, including but not limited to IFNULL, have specific use cases – we will dig into the use cases of IFNULL below.
Use Cases of the MySQL IFNULL Function
Once people use IFNULL, they often combine the function with something else. Here’s a good example of a SQL query that uses the IFNULL MySQL function:
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SELECT product_name, price * (stock_amount + IFNULL(Ordered, 0)) FROM products;
Take a close look at this query – it’s definitely not as complex as it sounds.
All we’re doing is selecting a product name together with the price and multiplying it by the stock amount plus the order amount. If the order amount is NULL, we multiply it by zero (“0”) – that’s the crux of the function and that’s why it’s there in the first place.
IFNULL, in and of itself, isn’t looking very “fancy” – we’ll agree on that one. The whole power of the function is unleashed when combined with other functions.
IFNULL vs COALESCE
IFNULL has a sister, too – her name is COALESCE. The COALESCE function is essentially the same as IFNULL too – to replace IFNULL, use COALESCE like this – in other words, simply replace IFNULL with COALESCE and you’re done:
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SELECT product_name, price * (stock_amount + COALESCE(Ordered, 0)) FROM products;
Other Flow Control Functions Explained
As we’ve already told you, the MySQL IFNULL function is not the only flow control function offered by database management systems. Other flow control functions include CASE and IF. Now, we will tell you a little about them as well.
Flow Control with CASE
The CASE function is used to go through specific conditions and return a specified value. Look through the example we've given you above – we use the CASE function with the WHEN|THEN|ELSE|END clauses. This function is primarily useful when you want to return some kind of value in case of a specific outcome. Here’s how to understand such a function:
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SELECT [columns]
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CASE
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WHEN [columns with an expression] THEN [outcome]
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…
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ELSE [different outcome]
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END
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FROM table;
Simple, yeah? Great – we also think so!
Flow Control with IF
Data flow can also be controlled with the IF() function. IF() is usually not used standalone, but as part of a SQL query. An example can be seen below:
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SELECT [columns], IF([column with an expression], “outcome in case of everything being
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true”, “outcome in case of everything being false”)
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FROM table;
In other words, we can specify a return value if the condition is TRUE, and also a return value if the condition is FALSE.
Controlling Data Flow with SQL Clients
Once you’re aware of what flow control functions are in MySQL, it’s time to keep a closer eye on your database instances, too: functions do their work internally, but for your databases to sing (for their queries to be quick, databases to be always available and secure), you need to employ tools made for that purpose.
You’re in luck because DbVisualizer is one of such tools – DbVisualizer offers a free trial to test the software out. The tool is used by some of the best and biggest software giants across the globe and is packed with features that let you work with any database management system imaginable. Specifically, DbVisualizer comes with a visual query builder and extensive data visualization capabilities while ensuring that all of your data stored in the software remains safe and secure.
If you’ve read this blog, you’re certainly interested in putting your databases onto the next level – why not explore the feature list and try it today?
Summary
The MySQL IFNULL function is one of the functions allowing us to control data flow within our database instances. The function can be used standalone, but most of its use cases stem from the fact that its power can be combined to work in conjunction with SELECT queries.
IFNULL also has a sister with a name of COALESCE – these two functions are essentially the same.
We hope that this blog has helped you better understand the value that IFNULL and other flow control functions can bring to your database architecture, and until next time.
Frequently Asked Questions
WhatIis IFNULL in MySQL?
IFNULL is a MySQL database function that returns a value if the given expression is NULL.
Is IFNULL, NULLIF, and COALESCE the same?
Yes, these three functions accomplish one and the same goal and their use case is exactly identical to one another as well.
When to use IFNULL?
IFNULL should be used whenever you find yourself in a situation where you need to return a value (say, “0”) in case something is NULL. See examples in this blog.
What are the other data flow control functions in MySQL?
Other MySQL data flow control functions include CASE and IF. CASE is used together with the WHEN|THEN|ELSE|END clauses meaning that WHEN a specific value is X, THEN we do Y, ELSE we do Z, and we END.
The IF function is just what it sounds like – it’s a function allowing us to do certain things IF a specified value is TRUE or FALSE.
