MySQL SQLLesson 24Free preview

MySQL Wildcards

This lesson is part of MySQL · All levels

Summary

Wildcard is a special character that represents one or more other characters in a search pattern, and is most often used with the LIKE operator. The two main wildcards in MySQL are the percentage (%) for zero or more characters, and the bottom line (_) for exactly one character. Using wildcards as large as a %-initiated pattern can cause MySQL to perform a full scan, making searches slower on large tables.

Key points

The percentage (%) represents zero, one, or more characters at a time
The bottom line (_) represents exactly one character at that position
Wildcard only means as a pattern when used in LIKE, not a comparison =
The pattern that the wildcard initiates tends not to use the index so it's slower on big data.

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