# How to use a calculated column to calculate another column in the same view

Use a **Common Table Expressions** (`WITH`

clause) to create a computation layer or inline the calculation in the final select. Compute the first calculated column, then reference it for the second calculation:

Here, **first_calc** is calculated in the CTE and reused in the main query for **second_calc**. This technique ensures correct sequencing of calculations while maintaining readability.

## Crafting queries efficiently

Things can get messy with complex SQL computations. Here are the tools to keep it tidy:

### Nested queries

If simplicity is the goal, a nested query does wonders:

### Cross apply in SQL Server

CROSS APPLY: Your handy sidekick when joining becomes a nuisance:

### Optimal use of functions

Using functions? Choose ones that don't slow things down:

## The delicate art of performance optimization

Performance can make or break your SQL queries, especially with calculated columns:

### When it pays to repeat calculations

If a calculation is light, it might not hurt to repeat it:

### Conditional play with case expressions

In SQL, we have case expressions where you set the calculation rules:

## Advanced computation techniques

For off-the-beaten-path scenarios, SQL stands ready:

### Leveraging APPLY in Oracle

It's called LATERAL in Oracle 12c+, but it's the same as SQL Server's APPLY:

### Use CTE with OFFSET/FETCH for pagination

With Common Table Expressions and OFFSET/FETCH, you get calculated columns and pagination all in one:

### Validating calculations with sample data

Insert mock data using INSERT INTO to validate your view's calculations:

Was this article helpful?