SQL _ Wildcard

What is the SQL _ Wildcard?

The SQL _ wildcard is used as a placeholder within the LIKE operator to represent a single character in a text or string search. It's commonly used in SQL for pattern matching to find rows in a database where a particular character at a specific position in a column value matches a specified pattern. The _ wildcard allows you to perform precise and flexible character-based searches within text or string data.

When you would use it

You would use the SQL _ wildcard when you need to search for rows in a database where a particular character or character sequence at a specific position within a column value matches a specified pattern. It is especially useful when you want to perform character-based pattern matching and need to specify the exact position of the character.

Syntax

The _ wildcard is typically used in conjunction with the LIKE operator. The syntax is as follows:

WHERE column_name LIKE pattern

• column_name: The name of the column you want to search in.
• pattern: The search pattern that may include _ as a wildcard.

Parameter values

• column_name: The name of the column in which you want to search.
• pattern: The pattern you want to match against, where _ represents a single character.

Example query

Suppose you have a table named "employees" with a column "employee_name," and you want to find employees whose last name starts with "S" and is followed by any single character. You can use the _ wildcard with the LIKE operator as follows:

SELECT employee_name
FROM employees
WHERE employee_name LIKE 'S_';

In this query, S_ represents an "S" followed by any single character.

Example table response

Assuming the "employees" table contains the following data:

| employee_name  |
| -------------  |
| John Smith     |
| Mary Johnson   |
| Sam Brown      |
| Alex Parker    |
| Sarah Adams    |

The query mentioned earlier would return the following result:

| employee_name  |
| -------------  |
| Sam Brown      |
| Sarah Adams    |

This result includes employees whose last names start with "S" and are followed by a single character.

Use cases

• Performing character-based searches within text or string columns.
• Finding rows where a specific character sequence occurs at a particular position.
• Creating precise text pattern matching conditions.

SQL languages this is available for

The _ wildcard with the LIKE operator is a widely supported feature and is available in most relational database management systems (RDBMS). It can be used in SQL systems such as MySQL, PostgreSQL, Oracle Database, SQL Server, SQLite, and others. The syntax and behavior are generally consistent across these systems, making it a versatile tool for character-based pattern matching in SQL.