Why Does Escaping Backslashes Differ Between MySQL's WHERE and LIKE Clauses?

Escape Characters in MySQL WHERE and LIKE Clauses

In MySQL, when searching for special characters like the backslash () in a WHERE clause, no additional escaping is required. However, for LIKE clauses, a double backslash () is necessary. This is due to MySQL's default use of as an escape character in LIKE statements.

Understanding WHY and HOW Escape Characters Work in WHERE and LIKE

In WHERE clauses, MySQL compares the specified value directly to the column value without further processing. Therefore, a single backslash () is sufficient to match the backslash character in the column.

In LIKE clauses, MySQL first strips any backslashes from the specified pattern. Then, during the pattern matching process, it removes the remaining backslashes. This double stripping process requires a double backslash () to escape the backslash character and allow it to be matched in the LIKE clause.

Example

The provided SQL query demonstrates the difference:

(SELECT * FROM `titles` WHERE title = 'test\')
UNION ALL
(SELECT * FROM `titles` WHERE title LIKE 'test\\')

Output:

| ID | TITLE |
--------------
| 1 | test\ |
| 1 | test\ |

The double backslash () is required in the LIKE clause to match the backslash in the column value.

Changing the Escape Character

If desired, you can change the escape character used in LIKE statements by specifying the desired character after the ESCAPE keyword:

SELECT * FROM `titles` WHERE title LIKE 'test\' ESCAPE '|'

In this case, the pipe (|) is used as the escape character, allowing a single backslash () to be matched in the LIKE clause.

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