How to Execute External SQL Queries Against Multiple Tables in Python?

Executing External SQL Scripts in Python

You are currently working on learning how to execute SQL queries within Python and have an external SQL file that creates and manipulates data in three tables: 'Zookeeper', 'Handles', and 'Animal'. Additionally, the file contains a series of queries to be executed against these tables.

The confusion arises when executing queries like the following from within Python:

--1.1

SELECT ANAME,zookeepid
FROM ANIMAL, HANDLES
WHERE AID=ANIMALID;

--1.2

SELECT ZNAME, SUM(TIMETOFEED)
FROM ZOOKEEPER, ANIMAL, HANDLES
WHERE AID=ANIMALID AND ZOOKEEPID=ZID
GROUP BY zookeeper.zname;

These queries are not creating tables but rather retrieving data, which requires a different approach than inserting or deleting data.

Solution

To execute these queries from within Python, you can make use of string formatting to dynamically replace the table name placeholder '%s' with the actual table name you want to query. Here's how you can modify your code:

result = c.execute("SELECT * FROM {} WHERE {} != {} AND {} != {};".format(table, column1, value1, column2, value2))

In this example, '{}' represents the placeholders for table, column1, value1, column2, and value2. You can then replace these placeholders with the appropriate values depending on the query you want to execute.

Alternative Method

An alternative method you could consider is defining a function that takes the table name and query as input, eliminating the need for string formatting. This approach offers more flexibility and readability.

def execute_query(table, query):
    result = c.execute(query.format(table))
    # Do something with the results

for table in ['ZooKeeper', 'Animal', 'Handles']:
    query = "SELECT * FROM {} WHERE {} != {} AND {} != {};"
    execute_query(table, query)

This approach allows you to execute queries based on different conditions without modifying the query itself.

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