The webpage explains the SQL WHERE clause, which is used to filter records in an SQL query. The WHERE clause helps select only those records that satisfy a specific condition. It's not limited to SELECT statements but is also used in UPDATE and DELETE statements.

Key points include:

• Syntax:

  SELECT column1, column2, ...
  FROM table_name
  WHERE condition;
  

• Text vs. numeric values:
  • Text values must be in single quotes (e.g., 'Mexico')
  • Numeric values are not quoted (e.g., CustomerID = 1)
• Example usage:
  • Select all customers from Mexico:

    SELECT *
    FROM Customers
    WHERE Country = 'Mexico';
    

• Operators in the WHERE clause:
  • =: Equal
  • >: Greater than
  • <: Less than
  • >=: Greater than or equal
  • <=: Less than or equal
  • <>: Not equal (may also be written as != in some SQL versions)
  • BETWEEN: Between a certain range
  • LIKE: Search for a pattern
  • IN: Specify multiple possible values for a column

There are sample tables, interactive examples, and a video to further illustrate usage. The summary of operators you selected provides a quick reference for conditional expressions in SQL WHERE clauses.[1]

1

SQL WHERE Clause

The SQL WHERE Clause

The WHERE clause is used to filter records.

It is used to extract only those records that fulfill a specified condition.

Select all customers from Mexico:

SELECT * FROM Customers  
WHERE Country='Mexico';

Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition;

Note: The WHERE clause is not only used in SELECT statements, it is also used in UPDATE, DELETE, etc.!

Demo Database

Below is a selection from the Customers table used in the examples:

Text Fields vs. Numeric Fields

SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

SELECT * FROM Customers  
WHERE CustomerID=1;

Operators in The WHERE Clause

You can use other operators than the = operator to filter the search.

Select all customers with a CustomerID greater than 80:

SELECT * FROM Customers  
WHERE CustomerID > 80;

The following operators can be used in the WHERE clause: