Filtering data using SQL

By defining specific criteria, users can utilize data filtering to reduce the number of results returned by their queries.

WHERE Clause

When filtering data in SQL, the WHERE clause is employed. The query must satisfy a defined criteria in order to provide the intended results. The following is the syntax for the WHERE clause:

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

Column1, Column2,..., are a list of columns from which data is to be retrieved in the syntax above, and table_name is the name of the table from which the data is to be retrieved. The requirement that must be satisfied for the query to produce the intended results is known as the condition. As an illustration, suppose you wish to extract all the records from the "customers" database that have customers with the last name "Smith".

Use following SQL statement:

SELECT * FROM customers WHERE last_name = 'Smith';

This query will return all the records from the "customers" table where the last name is "Smith".

LIKE Operator

The LIKE operator is another way to filter data in SQL. It is used to match a pattern in a string column.

The syntax for the LIKE operator is as follows:

SELECT column1, column2, ... FROM table_name WHERE column_name LIKE pattern;

Column1, Column2,..., are a list of columns from which data is to be retrieved in the syntax above, and table_name is the name of the table from which the data is to be retrieved. The pattern consists of a string pattern that must match.

For example, Retrieve all records from a table called "products" where the product name contains the word "soap".

Use following SQL statement:

SELECT * FROM products WHERE product_name LIKE '%soap%';

The query will return all records from the "products" table where the product name contains the word "soap".

IN Operator

The IN operator is another way to filter data in SQL. It is used to match a column to a set of values. The syntax for IN operator is as follows:

SELECT column1, column2, ... FROM table_name WHERE column_name IN (value1, value2, ...);

Columns 1, 2, and so forth are the columns you wish to retrieve data from in the syntax above, and table_name is the name of the table you want to do so. The collection of values that must match is indicated by the values included in brackets.

For example, Retrieve all records from a table called "orders" where the customer's state is either "HR" or "MH".

Use following SQL statement:

SELECT *

FROM orders WHERE customer_state IN ('HR', 'MH');

This search will get all records from the "orders" table where either "HR" or "MH" is the customer's state. The WHERE clause, LIKE operator, and IN operator are effective tools for limiting the outcomes of queries according to particular standards.