How Can I Correctly Use WHERE IN Statements in SQLite to Avoid Errors and SQL Injection?

Understanding "WHERE _ IN _" Statements

When using WHERE IN statements in SQLite, it's essential to understand the correct syntax and usage to avoid common errors.

The Syntax Issue

The example code provided results in a "ProgrammingError" because the number of bindings (parameters) provided does not match the number of placeholders (?) in the statement. SQLite expects a bind parameter (? or a positional parameter) for each item in the IN list.

Solution

To correct this issue, create sufficient bind parameters to match the list of variables. This can be achieved using string interpolation:

statement = "SELECT * FROM tab WHERE obj IN ({0})".format(', '.join(['?'] * len(list_of_vars)))
c.execute(statement, list_of_vars)

Avoiding SQL Injection

Contrary to the original code snippet, this method is secure against SQL injection attacks because the variables are properly bound to the SQL statement.

Performance Considerations

For large lists of variables, using a temporary table may be more efficient. Create a temporary table to hold the values, then use a JOIN against the temporary table rather than an IN clause with bind parameters.

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