Wed 07th Oct 2026

Coding Business Logic from First Principles: Translating Logic into SQL and JS

Software Architecture Database MySQL
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In this article, we’ll explore how grounding your business logic in set theory simplifies translating complex rules into clean, production code.

When developing an application there is usually specific business logic to apply. The logic mostly fits into boolean algebra or the set theory concept in computer science.


We’ll apply the logic using SQL queries and JavaScript if statements. We’ll assume the logic will apply to the SQL fields: is_active and is_premium which indicates if the user is active (ie currently online) and if the user is subscribed. In JavaScript, we’ll use isActive and isPremium to represent these same properties.


There’ll also be a venn diagram which is as below:

  1. Red outline circle represents the is_active portion of the data (or isActive for the case of JS)
  2. Green represents the is_premium portion of the data (isPremium for JS)
  3. Blue will mark the portion of the data which satisfies the logic


Venn diagram description


The “AND” Conditional

This is a condition which requires all evaluated conditions to be true.

In set theory, this is the intersection of the data.

A business use case would be: finding customers who are both currently active and paying for a premium subscription.

The venn diagram representation:


Conditional AND venn diagram representation


In SQL:

SELECT * FROM users WHERE is_active = TRUE AND is_premium = TRUE;

In JavaScript:

if (user.isActive && user.isPremium) {
// execute some block of code
}


The “OR” Conditional

This conditional requires at least one of the evaluated conditions to be true. This represents the union of two sets, capturing data that exists in either circle, including the overlap.

A sample business use case for this would be creating a broad marketing list of anyone who has shown intent by either being active recently or having a premium account.

It’s venn diagram representation would be:


Conditional OR venn diagram representation


A sample SQL query would be:

SELECT * FROM users WHERE is_active = TRUE OR is_premium = TRUE;

The JS would be:

if (user.isActive || user.isPremium) {
showCommunityBanner();
}


The “XOR” Conditional

This conditional requires exactly one of the conditions to be true, but not both. It represents the symmetric difference, capturing the outer crescents of the Venn diagram while omitting the overlapping center.

A practical use case is dentifying edge-case users, such as those who are paying for premium but aren't active, or those who are active but haven't upgraded yet.

It’s venn representation is as below


Conditional XOR venn diagram representation


The SQL equivalent:

SELECT * FROM users WHERE (is_active = TRUE AND is_premium = FALSE) OR (is_active = FALSE AND is_premium = TRUE);

Note: Some SQL dialects (like MySQL) have a built-in XOR operator, the most universal way to write it uses standard operators.

It’s JS conditional can be represented as in either of the following ways:

// Cleanest approach for strict booleans:
if (user.isActive !== user.isPremium) {
triggerNudgeRoutine();
}
// The traditional expanded logical approach:
if ((user.isActive && !user.isPremium) || (!user.isActive && user.isPremium)) {
triggerNudgeRoutine();
}


The “NOT” Conditional

This simply reverses the truth value of a single condition. It selects everything entirely outside a specific circle in a Venn diagram.

An application of this would be filtering out a specific segment, such as finding all users who are on the free tier.

It’s venn depiction is as below:


Conditional NOT venn diagram representation


Its SQL representation:

SELECT * FROM users WHERE NOT is_premium = TRUE;

The JS equivalent:

if (!user.isPremium) {
nudgeToSubscribe(); // of course spotify does this after every other two listens:)
}


The “NAND” Conditional

This requires that the conditions are not all true. It is the exact opposite of the AND conditional. It selects everything in the universe except the overlapping center of the Venn diagram.

The business use case would be excluding your ideal cohort (active premium users) to analyze the behavior of everyone else. (well you know, to get them to be ideal as upper management wants)

The venn depiction:


Conditional NAND venn diagram representation


The SQL:

SELECT * FROM users WHERE NOT (is_active = TRUE AND is_premium = TRUE);

The JS:

if (!(user.isActive && user.isPremium)) {
hideSupportWidget(); // well, you know why :)
}


The “NOR” Conditional

This requires that none of the conditions are true. It is the exact opposite of the OR conditional, selecting only the space entirely outside both circles of the Venn diagram.

The practical application of this is identifying completely disengaged users who are neither active nor paying.

The venn of it:


Conditional NOR venn diagram representation


The SQL:

SELECT * FROM users WHERE NOT (is_active = TRUE OR is_premium = TRUE);

The JS:

if (!(user.isActive || user.isPremium)) {
promptAccountDeletion(); // might be churn
}


The “XNOR” Conditional

It requires both conditions to have the exact same truth value ie either both are true, or both are false. It is the inverse of XOR, capturing only the overlapping center and the space completely outside both circles.

Its practical implementation would be in finding users whose engagement matches their payment status ie either they are fully bought in (active and paying) or completely churned (inactive and not paying), ignoring the in-between states.

The venn depiction


Conditional XNOR venn diagram representation


The SQL:

SELECT * FROM users
WHERE (is_active = TRUE AND is_premium = TRUE)
OR (is_active = FALSE AND is_premium = FALSE);

Note: In many SQL dialects, this can be written much more succinctly as WHERE is_active = is_premium.

The JS:

// Cleanest approach for strict booleans:
if (user.isActive === user.isPremium) {
logStandardState();
}
// The traditional expanded logical approach:
if ((user.isActive && user.isPremium) || (!user.isActive && !user.isPremium)) {
logStandardState();
}


The “BUF” Conditional

In digital logic, a buffer simply takes an input and passes it through unchanged. In a database context, this is the evaluation of a single, standalone baseline condition without any combinational logic.

Its business use case is a simple, direct filter, such as querying all active users regardless of any other status.

The Venn:


Conditional BUF venn diagram representation


Its SQL:

SELECT * FROM users WHERE is_active = TRUE;

In JS:

if (user.isActive) {
showGreenOnlineDot();
}


Conclusion

Every business requirement, no matter how complex, ultimately reduces to a set of evaluated truth values. While most developers routinely rely on standard AND and OR operations, limiting your database queries to basic conditionals misses the expressive power of formal Boolean algebra. Understanding how hardware-level logic gates—such as exclusive disjunctions (XOR), equivalences (XNOR), and inverted sets (NAND/NOR)—map directly to SQL WHERE clauses and application state management allows you to write cleaner, more intuitive code.


By grounding your database logic in set theory and logic gate architecture, you eliminate redundant checks, avoid edge-case bugs, and create queries that are mathematically provable. The next time you need to write complex conditional logic, step back from the code editor, map out the truth table or Venn diagram, and let formal logic guide your query structure.

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