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I have a code like the following:

   sql_command='''SELECT Grade From GRADES where Student_Number='''+str(id) +''' AND Course_ID IN'''+(list)
   grades=execute_sql(sql_command,sql_cursor)

where the list is the a list containing elements in the course_id column satisfying a condition (specific course id),

I want to say, select the only grade where the course_id column is the course_id in my list. How do I do that?

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3 Answers 3

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You want to join all elements in the list into one string, e.g.:

sql_command ='''SELECT Grade From GRADES where Student_Number='''+str(id) 
sql_command+=''' AND Course_ID IN ('''+ ','.join(list) + ''')'''
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2 Comments

the list contains tuples, not str.... is it the same thing to do or ?@EricBouwers
That was not clear to me from the question. Assuming that one of the tuple values contains the course id you are interested in you can create a new list with only those values using the answer to this question
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A couple of things:

  • Assuming ID is coming from a user's input, this script is going to have being vulnerable to a SQL injection attack. See here for an example of using parameters, which are safer.

  • The solution to your specific question involves imploding your list:

    format_strings = ','.join(['%s'] * len(list))

Source: imploding a list for use in a python MySQLDB IN clause

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0

Here is how it can be done using sqlite3

cursor.execute(
    "SELECT Grade From GRADES where Student_Number= ? AND Course_ID IN (?)",
    (id, ','.join(map(str, list)))
)

Please don't use %s as its not recommended. Check sqlite3 documentation for more.

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1 Comment

the list contains tuple,not str, is it the same thing to write?@Stephan

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