Pattern Matching in SQL Pattern Matching Operators

SQL pattern matching operators are used to match patterns within strings in SQL queries. The following operators are commonly used for pattern matching in SQL:

1. LIKE operator: The LIKE operator is used to match a character pattern to a string. It uses two special characters to match patterns: "%" (percent sign) and "_" (underscore).

Syntax:

SELECT column_name(s) 
FROM table_name 
WHERE column_name LIKE pattern;

Example:

SELECT *
FROM employees
WHERE employee_name LIKE 'John%';

Output:

employee_id	employee_name
1	John Smith
4	John Doe
6	John Johnson

Explanation:

In the above example, the LIKE operator is used to retrieve all the employees whose name starts with "John". The "%" symbol is used to match any number of characters at the end of the string.

2. REGEXP operator: The REGEXP operator is used to match a regular expression pattern to a string.

Syntax:

SELECT column_name(s) 
FROM table_name 
WHERE column_name REGEXP pattern;

Example:

SELECT *
FROM products
WHERE product_name REGEXP '^Apple.*Phone$';

Output:

product_id	product_name
2	Apple iPhone 11
3	Apple iPhone 12
5	Apple iPhone SE
7	Apple iPhone XR
8	Apple iPhone XS Max

Explanation:

In the above example, the REGEXP operator is used to retrieve all the products whose name starts with "Apple" and ends with "Phone". The "^" symbol is used to match the beginning of the string, and the "$" symbol is used to match the end of the string.

Use

Pattern matching operators are used to retrieve specific data from a database that matches a given pattern. They are commonly used in where clauses of SQL queries.

Important Points

• The LIKE operator is case-sensitive by default.
• The REGEXP operator is case-insensitive by default.
• The "%" and "_" symbols can be escaped using "".
• The "^" and "$" symbols are used to match the beginning and end of the string respectively.

Summary

Pattern matching operators in SQL are used to match patterns within strings. The LIKE operator is used to match a character pattern to a string, while the REGEXP operator is used to match a regular expression pattern to a string. The operators are commonly used in where clauses of SQL queries to retrieve specific data from a database that matches a given pattern.