SQL Database Tutorial: Mastering Data Comparison Techniques51

Welcome to this comprehensive tutorial on data comparison within SQL databases. Efficiently comparing data is a crucial skill for any database administrator, data analyst, or developer working with SQL. This guide will cover various techniques, from simple comparisons using `WHERE` clauses to more advanced methods like using joins and set operations. We'll walk through practical examples using common SQL dialects, ensuring you're equipped to handle a wide range of data comparison scenarios.

Fundamental Comparisons: The WHERE Clause

The most basic way to compare data in SQL is using the `WHERE` clause. This clause allows you to filter rows based on specified conditions. Let's consider a simple table named `Customers` with columns `CustomerID`, `Name`, and `City`.

To find all customers from 'London', you would use:```sql
SELECT * FROM Customers WHERE City = 'London';
```

This uses the equality operator (`=`). You can also use other comparison operators:* `!=` or ``: Not equal to
* `>`: Greater than
* `=`: Greater than or equal to
* `

2025-04-21

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