How do I pass parameters to Pandas\' read_sql with SQL queries?

Passing Parameters in Pandas' read_sql with SQL Queries

When using Pandas to perform SQL queries with parameters, there are two main approaches: passing parameters as a list or tuple, or passing them as a dictionary.

Passing Parameters as a List or Tuple

The first method involves creating a SQL query with placeholders, such as BETWEEN %s AND %s, and passing the parameter values as a list or tuple. This can be seen in the following 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>

Passing Parameters as a Dictionary

The second method involves creating a SQL query with named parameters, such as BETWEEN :dstart AND :dfinish, and passing the parameter values as a dictionary. However, it's important to note that not all database drivers support named parameters.

For example, psycopg2, which is commonly used with PostgreSQL, supports the %(name)s style of named parameters. Here's an example:

<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>

Remember to check the documentation for your chosen database driver to determine the supported syntax for named parameters.

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