How can I pass parameters to an SQL query using Pandas\' read_sql method with SQLAlchemy?

Parameters in Pandas' read_sql Query with SQLAlchemy

When working with an SQLAlchemy engine to connect to a database, parameters can be passed in an SQL query using Pandas' read_sql method. There are two primary approaches to achieve this, as outlined below.

Using a List or Tuple

This method involves creating a list or tuple containing the values to be passed to the query. The placeholder for these values in the SQL statement should be question marks (?). For example:

<code class="python">df = psql.read_sql(('select "Timestamp", "Value" from "MyTable" '
                     'where "Timestamp" BETWEEN %s AND %s'),
                   db,params=[datetime(2014,6,24,16,0),datetime(2014,6,24,17,0)],
                   index_col=['Timestamp'])</code>

Using a Dictionary

Alternatively, a dictionary can be used to pass parameters by specifying the parameter names and their corresponding values. However, the specific syntax used for parameter placeholders may vary depending on the database driver. In the case of psycopg2, the preferred syntax is to use the %(name)s format.

<code class="python">df = psql.read_sql(('select "Timestamp", "Value" from "MyTable" '
                     'where "Timestamp" BETWEEN %(dstart)s AND %(dfinish)s'),
                   db,params={"dstart":datetime(2014,6,24,16,0),"dfinish":datetime(2014,6,24,17,0)},
                   index_col=['Timestamp'])</code>

It's important to note that the supported parameter syntax will vary based on the database driver being utilized. Therefore, it's recommended to consult the documentation for the specific driver to ensure proper usage.

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