MySQL Cookbook

Chapter 10. Importing and Exporting Data

Introduction

Suppose you have a file named somedata.csv that contains 12 columns of data in comma-separated values (CSV) format. From this file you want to extract only columns 2, 11, 5, and 9, and use them to create database records in a MySQL table that contains name, birth, height, and weight columns. You need to make sure that the height and weight are positive integers, and convert the birth dates from MM/DD/YY format to CCYY-MM-DD format. How can you do this?

In one sense, that problem is very specialized. But in another, it’s not at all atypical, because data transfer problems with specific requirements occur frequently when transferring data into MySQL. It would be nice if datafiles were always nicely formatted and ready to load into MySQL with no preparation, but that is frequently not so. As a result, it’s often necessary to preprocess information to put it into a format that MySQL finds acceptable. The reverse also is true; data exported from MySQL may need massaging to be useful for other programs.

Some data transfer operations are so difficult that they require a great deal of hand checking and reformatting, but in most cases, you can do at least part of the job automatically. Virtually all transfer problems involve at least some elements of a common set of conversion issues. This chapter discusses what these issues are, how to deal with them by taking advantage of the existing tools at your disposal, and how to write your own ...