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POHow to iterate through a MySQL table with Python?
 

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  1. POHow to iterate through a MySQL table with Python?
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    <p>I have a Python script which uses the MySQLdb interface to load various CSV files into MySQL tables.</p> <p>In my code, I use Python's standard CSV library to read the CSV, then I insert each field into the table one at a time, using an <code>INSERT</code> query. I do this rather than using <code>LOAD DATA</code> so that I can convert null values and other minor clean-ups on a per-field basis.</p> <p>Example table format:</p> <pre><code>`id_number` | `iteration` | `date` | `value` 102 | 1 | 2010-01-01 | 63 102 | 2 | 2010-01-02 | NULL 102 | 3 | 2010-01-03 | 65 </code></pre> <p>The null value in the second iteration of <code>id_number = 102</code> represents a case where <code>value</code> hasn't changed from the previous day i.e. <code>value</code> remains 63.</p> <p>Basically, I need to convert these null values to their correct values. I can imagine 4 ways of doing this:</p> <ol> <li><p>Once everything is inserted into the table, run a MySQL query that does the iterating and replacing all by itself.</p></li> <li><p>Once everything is inserted into the table, run a MySQL query to send some data back to Python, process in Python then run a MySQL query to update the correct values.</p></li> <li><p>Do the processing in Python on a per-field basis before each insert.</p></li> <li><p>Insert into a temporary table and use SQL to insert into the main table.</p></li> </ol> <p>I could probably work out how to do #2, and maybe #3, but have no idea how to do #1 or #4, which I think are the best methods as it then requires no fundamental changes to the Python code.</p> <p>My question is A) which of the above methods is "best" and "cleanest"? (Speed not really an issue.) and B) how would I achieve #1 or #4?</p> <p>Thanks in advance :)</p>
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    1. COAdd 4) insert into a temporary table and use SQL to insert into the main table
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    2. COThanks, I've added that in. I wouldn't know how to do that either, as it's my SQL that's lacking :(
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