MySQL Cookbook

10.44 Epilog

Recall the scenario with which this chapter began:

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?

So ... how would you do that, based on the techniques discussed in this chapter?

Much of the work can be done using the utility programs developed here. You can convert the file to tab-delimited format with cvt_file.pl, extract the columns in the desired order with yank_col.pl, and rewrite the date column to ISO format with cvt_date.pl:

% cvt_file.pl --iformat=csv somedata.csv \
    | yank_col.pl --columns=2,11,5,9 \
    | cvt_date.pl --columns=2 --iformat=us --add-century > tmp

The resulting file, tmp, will have four columns representing the name, birth, height, and weight values, in that order. It needs only to have its height and weight columns checked to make sure they contain positive integers. Using the is_positive_integer( ) library function from the Cookbook_Utils.pm module file, that task can be achieved using a short special-purpose script that isn't much more than an input loop:

#! /usr/bin/perl -w
# validate_htwt.pl - height/weight validation example

# Assumes tab-delimited, linefeed-terminated input lines.

# Input columns and the actions to perform on them are as follows:
# 1: name; echo as given
# 2: birth; echo as given
# 3: height; validate as positive integer
# 4: weight; validate as positive integer

use strict;
use lib qw(/usr/local/apache/lib/perl);
use Cookbook_Utils;

while (<>)
{
    chomp;
    my ($name, $birth, $height, $weight) = split (/\t/, $_, 4);
    warn "line $.:height $height is not a positive integer\n"
                                if !is_positive_integer ($height);
    warn "line $.:weight $weight is not a positive integer\n"
                                if !is_positive_integer ($weight);
}

exit (0);

The validate_htwt.pl script doesn't produce any output (except for warning messages), because it doesn't need to reformat any of the input values. Assuming that tmp passes validation with no errors, it can be loaded into MySQL with a simple LOAD DATA statement:

mysql> LOAD DATA LOCAL INFILE 'tmp' INTO TABLE  tbl_name ;