How to write not equal to a certain condition in sql

In SQL, the "<>" operator is used to express "not equal to" a certain condition. The syntax is: SELECT FROM table_name WHERE column_name <> value. For example: to find customers whose name is not equal to "John Doe": SELECT FROM customers WHERE name <> 'John Doe'; to find products whose price is not equal to 100: SELECT * FROM products WHERE price <> 100.

How to use SQL to express "not equal to" a certain condition

In SQL, use "<> ;" operator means "not equal to".

Syntax:

<code>SELECT * FROM table_name WHERE column_name <> value</code>

The following example demonstrates how to use the "<>" operator:

<code>-- 查找所有姓名不为 "John Doe" 的客户
SELECT * FROM customers WHERE name <> 'John Doe';

-- 查找所有价格不为 100 的产品
SELECT * FROM products WHERE price <> 100;

-- 查找所有订单日期不为 "2023-03-08" 的订单
SELECT * FROM orders WHERE order_date <> '2023-03-08';</code>

Other notes:

• The "<>" operator can also be used to compare NULL values. For example, the following query returns all customers with non-NULL names:

<code>SELECT * FROM customers WHERE name <> NULL;</code>

• When using the "<>" operator, make sure the data types match. For example, if "column_name" is a string, then "value" must also be a string.

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