Return 0 if field is null in MySQL

Handling multiple-null-field scenarios

Dealing with multiple fields in a query that can potentially contain null values? No worries! By applying IFNULL() on each field, we can ensure all the subtotals are calculated accurately as shown below:

SELECT
  product_name AS `You get:`,
  quantity AS `This many:`,
  IFNULL(price, 0) AS `For just:`,
  quantity * IFNULL(price, 0) AS `Total cost: 👀`
FROM orders;
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Performance considerations

If your database is read-heavy, consider optimizing it by storing already computed values in an extra column or via a trigger. This bypasses the need for the IFNULL() or COALESCE() operations in every query.

Reducing computation time = Saving global CPU cycles = Saving planet 🌏 (Hey! We just turned software optimization into environmental activism!)

Coating the SUM function for precise computation

When performing SUM() on a bunch of null values, the operation might just return a null feeling of despair. Use IFNULL() to save the day and achieve precise results:

SELECT SUM(IFNULL(column_name, 0)) AS `Total: no nulls invited!`
FROM your_table;
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Fear no empty string

Empty strings can lurk around like unseen ninjas, sometimes as problematic as null values. Let's illuminate them with our SQL flashlight:

SELECT IFNULL(NULLIF(column_name, ''), 0) FROM your_table;
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This pattern transforms an empty string into a null, which in turn gets replaced by 0. Dealt with, in one fell swoop!

Conquer nulls in subqueries and joins

null values have a knack for creeping in subqueries or joins. Implement IFNULL where null values might rear their null heads:

SELECT a.id, IFNULL(b.total, 0) AS `Total: nulls not included!`
FROM table_a AS a
LEFT JOIN (SELECT id, SUM(value) AS total FROM table_b GROUP BY id) AS b
ON a.id = b.id;
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Options, trade-offs and alternatives

Getting bored of IFNULL and COALESCE? How about the idea of using a view or a computed column? Some databases support these features, and they encapsulate computations nicely, making queries cleaner and more maintainable.