[MySQL must know and know (5)] [Use wildcards to filter]

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One, the LIKE operator

Wildcard: a special character used to match part of a value

Search mode: search conditions composed of literal values, wildcards, or a combination of both

The wildcard itself is actually a character with special meaning in the WHERE clause of SQL

1.1 Percent sign wildcard

The most commonly used wildcard is the percent sign. In the search string,% means any character appears any number of times

mysql> SELECT prod_id, prod_name
    -> FROM products
    -> WHERE prod_name LIKE 'jet%';

Case sensitive

Depending on how MySQL is configured, searches can be case sensitive. 'jet%' and JetPack 1000 will not match

Wildcards can be used anywhere in the search pattern

mysql> SELECT prod_id, prod_name
    -> FROM products
    -> WHERE prod_name LIKE '%anvil%';

Wildcards can also appear in the middle of the search pattern

mysql> SELECT prod_name
    -> FROM products
    -> WHERE prod_name LIKE 's%e';

Pay attention to trailing spaces.
Trailing spaces may interfere with wildcard matching. A good way is to use functions

Note that NULL
seems to match anything with% wildcards, but there are exceptions, namely NULL

1.2 Underscore wildcard

The underscore value matches a single character instead of multiple characters

mysql> SELECT prod_id, prod_name
    -> FROM products
    -> WHERE prod_name LIKE '_ ton anvil';

mysql> SELECT prod_id, prod_name
    -> FROM products
    -> WHERE prod_name LIKE '% ton anvil';

2. Skills of using wildcards

1. Don't overuse wildcards
2. When you really need to use wildcards, don't use them at the beginning of the search pattern unless necessary
3. Pay careful attention to the position of wildcards

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Next: [MySQL must know and know (6)] [Search with regular expressions]