How Can I Use Special Characters Effectively in SQL LIKE Clauses for Pattern Matching?

Comprehensive List of Special Characters for SQL LIKE Clause

In the context of SQL queries, the LIKE clause provides a powerful tool for performing pattern-based searches. To cater to a wide range of pattern matching requirements, various SQL dialects support a comprehensive set of special characters.

Common Special Characters

Across most SQL dialects, several common special characters are employed for pattern matching:

• % (Percent Sign): Represents any string of zero or more characters.
• _ (Underscore): Matches any single character.
• [] (Square Brackets): Encloses character ranges or specific characters for matching.

Database-Specific Variations

In addition to these common characters, certain databases offer additional capabilities:

SQL Server:

• **[specifier]: Matches a single character within the specified range (e.g., [a-z]).
• **[^specifier]: Matches a single character outside the specified range.
• ESCAPE clause: Allows specifying a character to escape the literal meaning of other special characters.

MySQL and Oracle:

• ESCAPE clause: Similar to SQL Server's ESCAPE clause.

PostgreSQL:

• SIMILAR TO operator: Extends LIKE functionality with additional modifiers such as:

  • []: As in SQL Server.
  • |: Match either of two alternatives.
  • *: Repeat the previous item zero or more times.
  • : Repeat the previous item one or more times.

ANSI SQL92:**

• ESCAPE clause: Optional, if specified.

Example Usage

In SQL Server:

SELECT Name FROM Person WHERE Name LIKE '%Jon%'

finds all names containing "Jon" anywhere.

In PostgreSQL using the SIMILAR TO operator:

SELECT Name FROM Person WHERE Name SIMILAR TO 'J[ao]'

matches all names starting with either "Ja" or "Jo".

By leveraging the special characters supported by various SQL dialects, developers can construct highly flexible and efficient pattern matching queries.

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