How Can I Safely Use Python String Formatting with SQL Wildcards and LIKE Statements?

Using Python String Formats with SQL Wildcards and LIKE

SQL statements that utilize wildcards and the LIKE keyword can encounter challenges when employing Python's string formatting capabilities. Here are some common pitfalls and their potential solutions:

Attempt 1 and Attempt 2: % Format String with Wildcards

Directly using the % string formatting with wildcards can lead to errors. Python's string formatting does not recognize the special characters used for wildcards, resulting in the error "unsupported format character ''' (0x27) at index 128."

Attempt 3: Concatenating Strings

While concatenating strings may appear to resolve the formatting issue, it actually creates a syntax error when used with MySQLdb due to line 158 in the "cursors.py" file. The error "query = query % db.literal(args)" indicates a mismatch in the number of arguments provided.

Attempt 4: Using the % Escape Sequence

Using the '%%' escape sequence may also result in the same error as attempt 3.

Secure Solution with Execute() and Query Parameters

To mitigate security concerns from SQL injection attacks, it is advisable to use the execute() method with query parameters. This approach ensures proper handling of wildcard characters and prevents malicious input.

For instance, the following code demonstrates a secure implementation:

curs.execute("""SELECT tag.userId, count(user.id) as totalRows 
FROM user 
INNER JOIN tag ON user.id = tag.userId 
WHERE user.username LIKE %s""", ('%' + query + '%',))

In this example, two arguments are passed to the execute() method. The first argument contains the parameterized query, while the second one provides the wildcard-formatted value as a tuple. This approach ensures a secure and efficient execution of the SQL statement with wildcards.

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