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After hours of unsuccessfully trying to fetch a row from my MySQL DB and saving the output to a string array, I finally decided to come here and ask for help, because I apparently can't solve it myself. This is no homework, I am merely trying to write a simple command line mysql-client that can be integrated into other C projects. As I am not extracting integers from the DB, I can't work with atoi :(

My problem is that I am not able to use sprintf() in order to write the value of row[0] into a field_array[i], because unlike I thought, row[] is not being incremented on every call to mysql_fetch row(). Actually, when calling this command, row[0] only gets updated with the content of the MYSQL_RES *struct.current_row, in this case MYSQL_RES *headers.current_row. Thus the problem is that I want to be able to call mysql_fetch_row() normally, whilst incrementing the int i for the field_array[i] to be able to successfully sprintf() all values.

Below, the relevant code. If anything is missing, please tell me :)

Used variables:

MYSQL_ROW row;
MYSQL_RES *headers;
char field_array[50][100];

Part of the code which I don't get to work as intended:

while ((row = mysql_fetch_row(headers)))
 {
     for(int i = 0; i < num_fields; i++)
     {
        printf("%s\n", row[i] ? row[i] : "NULL");
        sprintf(&field_array[i], "%s", row[i]);
     }
 }

Please help me, if possible. I am using the Connector/C MySQL API, working on a windows 7 x64 environment with mingw32/GCC (Code::Blocks).

My intention is to write all values into field_array to work with them later on.

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  • What is the problem? You didn't say. And you couldn't find any examples in your book? Commented Nov 19, 2015 at 22:10
  • Well the problem was that I was not able to sprintf() the value of row[0] into field_array[i] because row[0] is not incremented, but replaced on every call to mysql_fetch_row(). But I didn't know that at that point so I didn't even know what the real problem was :) Commented Nov 19, 2015 at 23:05
  • Then you were not ready to post a question on SO! Please edit the problem into the question to prevent closure/deletion. Commented Nov 20, 2015 at 10:04
  • Oh well, actually I thought I described it in the first sentence, where I said "unsuccessfully trying to fetch a row from my MySQL DB and saving the output to a string array". Commented Nov 20, 2015 at 13:46
  • 1
    much much much much much better thanks Commented Nov 20, 2015 at 14:07

1 Answer 1

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Okay, I solved it by myself. The point was to use the array-increment within the while() loop instead of the for() loop.

Now I fetch all row values and write them into my field_array, which can then be used in the rest of the function.

For everyone having the same problem and finding this topic, here is your answer!

    while ((row = mysql_fetch_row(headers)))
    {
        for(int i_row = 0; i_row < num_fields; i_row++)
        {
            if (row[i_row])
            {
                sprintf(&field_array[i_array][0], "%s", row[i_row]);
            }
            else
            {
                printf("NULL");
            }
        }
        i_array++;
    }

To demonstrate the correctly working array, I used

for (int i = 0; i < (*headers).row_count; i++)
{
    printf("%s\n", field_array[i]);
}
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1 Comment

You didn't actually tell anyone what the problem was, so the chance of anyone finding this is minimal. Thanks for posting the answer, though!

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