Can I parameterize the table name in a prepared statement?

sql

sql-injection

dynamic-sql

security-best-practices

byAnton Shumikhin·Dec 9, 2024

In prepared statements, you can't use variable (parameterize) table names as they're finalized at compile time. You could employ dynamic SQL, but tread cautiously to avert SQL injection. Always reassure security by whitelisting table names and making use of QUOTENAME:

IF @tableName IN (SELECT tableName FROM whitelist)
BEGIN
    SET @sql = N'SELECT * FROM ' + QUOTENAME(@tableName) + ' WHERE Condition = @param';
    EXEC sp_executesql @sql, N'@param VARCHAR(255)', @param = 'value'; -- Avoid SQL injection like a boss 💪
END;

The approach illustrated above utilizes a validated list (whitelist) and binds parameters (@param) for non-structural parts, giving balance between security and adaptability.

Deep dive into parameterizing table names

Dynamic SQL - A double-edged sword

Dynamic SQL grants you the ability to form SQL commands as strings and then execute them. This feature opens up the possibility for variable table name selection but with a catch - potential increase in risk of SQL injection. Always proceed with caution!

SET @sql = N'SELECT * FROM ' + @tableName + 'WHERE ...'; -- Not if @tableName came directly from user input!

Safe handling of user input - No shortcuts!

Never let your guards down when dealing with user input. Before feeding any input to SQL, validate and sanitize them properly. Draw a mapping between user inputs and pre-defined, valid table names. Remember, your database, your rules!

string userTable = GetUserTableInput(); // The Trojan Horse
string safeTable = GetSafeTableName(userTable); // Checkmate! Tables turned. Literally.

Application logic: The real puppet master

As a best practice, keep your SQL logic decoupled from user influence. Let backend logic determine table names based on business rules. Users can suggest, but you decide!

def get_table_name(user_choice):
    # Use application rules, not user inputs, for choosing the table
    table_mapping = {'option1': 'Table_A', 'option2': 'Table_B'}
    return table_mapping.get(user_choice, 'default_table') -- User's wish, your command.

Research for the win

Every programmer's best friend is his/her will to research. Invest your time to understand the ins and outs of dynamic SQL and dig into SQL injection prevention. Online resources from OWASP and other security guidelines contain treasure troves of knowledge to write secured dynamic SQL.

Pro tips to safely deal with dynamic SQL

Keep a strict whitelist handy

Maintain a well-documented safelist of permitted tables and check inputs against it:

IF EXISTS (SELECT 1 FROM safelist WHERE tableName = @input) -- I trust you but I'll verify first
SELECT [...] FROM Table_X WHERE id = @value -- I know what I'm doing here

Special functions to the rescue

Generic methods are not always enough. Make use of database-specific functions for secured handling:

SQL Server: QUOTENAME(@tableName) -- No tableName, No worries
MySQL: CONCAT('', REPLACE(@tableName, '', '``'), '')` -- Table Names can't scare me
PostgreSQL: quote_ident(@tableName) -- Postgres? Sure, why not.

To err is human

In the world of programming, a sense of safety can often lead to complacency. Keep yourself updated about security updates and best practices. Don't shy away from auditing your dynamic SQL strategies regularly.

explain-codes / Sql / Can I parameterize the table name in a prepared statement?

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