How Can I Effectively Execute Parameterized SQL Queries in Python Using Variables?

Parameterized SQL queries and effective use of variables in Python

Storing SQL queries in variables improves code flexibility and readability. This article explores how to leverage variables to efficiently execute parameterized SQL queries in Python.

Understanding parameterized SQL queries

Parameterized SQL queries prevent SQL injection by separating SQL statements from variable data. In Python, this is achieved through the cursor.execute() method, where the placeholder (%s) represents the variable.

Variable assignment

To store the SQL query in a variable, assign it to a string variable, for example:

<code class="language-python">sql = "INSERT INTO table VALUES (%s, %s, %s)"</code>

Execute queries using multiple variables

To perform a parameterized query with multiple variables, pass the variables as a sequence or map. However, the execute() method expects three parameters, and containing a SQL query exceeds this limit.

Solution: Split variables

To solve this problem, SQL queries and variables can be split into separate variables and parameters. One way is to assign the variable to the element of the tuple:

<code class="language-python">sql_and_params = ("INSERT INTO table VALUES (%s, %s, %s)", var1, var2, var3)</code>

However, this method throws an error due to the number of parameters. Instead, when passing it to execute(), the tuple should be split as follows:

<code class="language-python">cursor.execute(sql_and_params[0], sql_and_params[1:])</code>

Alternative: separate variables

A more readable approach is to use separate variables for the SQL query and its parameters:

<code class="language-python">sql = "INSERT INTO table VALUES (%s, %s, %s)"
args = var1, var2, var3
cursor.execute(sql, args)</code>

This method provides a clear separation between the SQL statement and its parameters.

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