"MySQL is better than know." The eighth chapter is filtered with a wildcard character

1. Like operator

Previously used operators are for known data, and wildcard characters can also be used to search for unknown data.

wildcard character (wildcard): used to match Special characters that are worth a portion.

Search pattern: A search condition consisting of a literal value, a wildcard character, or a combination of both.

To use a wildcard character for a search clause, you must use the LIKE operator because it indicates MySQL, followed by a wildcard match instead of a direct equality match.

predicate: When an operator acts as a predicate, it is no longer an operator and like is a predicate.

2, percent semicolon wildcard character%

% indicates any number of occurrences of any character.

Input: SELECT prod_id,prod_name

From Products

WHERE prod_name like ' jet% ';

Analysis: Show two columns-Product ID and name, table source-products, filter terms the product name first three characters is jet (regardless of case, but the search mode can be set case-insensitive, not set here).

Note: Wildcards can appear anywhere in the search mode, the number is arbitrary, such as: Like '%jet% ', such as ' s%e ', wildcard characters in addition to one or more characters, can also match 0 characters, so the wildcard range is actually 0-∞. Wildcard characters cannot match null.

3, underline the wildcard character (_)

The underscore wildcard can match only one character.

4. Tips for using wildcard characters

Do not overuse wildcard characters, which are at the cost of performance.

Be sure to use a wildcard character, and do not place it at the beginning of the search pattern.

"MySQL is better than know." The eighth chapter is filtered with a wildcard character