Usage of multiple fields in sql

There are two ways to use the IN operator for multiple fields in SQL: through a subquery or directly listing multiple values. Subqueries are used to retrieve values ​​from other queries, while multiple values ​​can be listed directly separated by commas. The IN operator checks whether a given value is in the list of specified values.

IN usage in multiple fields in SQL

IN operator is used to check whether a given value is in in a list of specified values. When you need to check multiple fields, you can use a subquery or multiple values ​​in the IN operator.

Subquery

A subquery is a nested query used to retrieve data from a database. It can be used within the IN operator to compare the values ​​of multiple fields against it. The syntax is as follows:

<code class="sql">SELECT * FROM table_name
WHERE (column1, column2, ...) IN (
    SELECT column1, column2, ... FROM subquery
);</code>

For example:

<code class="sql">SELECT * FROM orders
WHERE (order_id, customer_id) IN (
    SELECT order_id, customer_id FROM order_details
);</code>

Multiple values

You can also specify multiple values ​​in the IN operator, separated by commas. The syntax is as follows:

<code class="sql">SELECT * FROM table_name
WHERE (column1, column2, ...) IN (value1, value2, ...);</code>

For example:

<code class="sql">SELECT * FROM customers
WHERE (first_name, last_name) IN ('John', 'Doe');</code>

Example

Consider a table containing the following dataorders:

##10112011021301103 22011042302

order_id	customer_id	product_id

To find out the customers who ordered product 201 or 302, you can use the IN operator:

<code class="sql">SELECT * FROM orders
WHERE (product_id) IN (201, 302);</code>

The output will be:

order_idcustomer_idproduct_id##101102103##1042302

1	201
1	301
2	201

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