I want to make Inserts on mysql database,having as values,some string,chars...
This works:
if (mysql_query(con, "INSERT INTO Cars VALUES(2,'Mercedes',57127)")) {
finish_with_error(con);
}
How can I do something like this?
char str[]="Mercedes";
if (mysql_query(con, "INSERT INTO Cars VALUES(2,str,57127)")) {
finish_with_error(con);
}
In working in C.
You need to concatenate the two "strings" before passing them down into the library.
Either using the pre-processor:
#define str "Mercedes"
...
if (mysql_query(con, "INSERT INTO Cars VALUES(2,"str",57127)")) {
finish_with_error(con);
}
Or do it during runtime:
char str[] = "Mercedes";
char query_template[] = "INSERT INTO Cars VALUES(2,%s,57127)"
char query[sizeof str + sizeof query_template - 3];
sprintf(query, query_template, str);
if (mysql_query(con, query, )) {
finish_with_error(con);
}
Note: The latter solution introduces a security issue if the content of str is provided externally. Do not do this in production code then.
try this
int id=1,price=123435;
char name[]="mercedez";
char consulta[1024];
sprintf(consulta,"insert into cars values('%d','%s','%d')",id,name,price);
if(mysql_query(con,consulta)==0)
fprintf(stdout,"datos insertados con exito\n");
Try this:
char str[] = "Mercedes";
response = mysql_query("INSERT INTO cars (column1,column2,column3) VALUES 2,'str',57127)");
if(response){ finish_with_error(con); }
Related
I load a dictionary and made many manipulation in it. To save some CPU time, I actually store the result into a flat file for future use. How can I store that memory structure into a BLOB columns of MariaDB database (program in C)
He is my actual code et what an example of what I try to do.
//--- Global variables and CONST for databases
#define DB_NAME "some_name"
#define DB_USER "admin"
#define DB_PWD "qwerty"
#define DB_SERVER "localhost"
MYSQL *conn;
MYSQL_RES *res;
MYSQL_ROW row;
int main (int argc, char **argv)
{
char str_query [2048] ;
//----------------------------------------------------------------
// The way I dump the memory (structure) into a flat file actually
//----------------------------------------------------------------
fd = fopen("./mem_dump.binary","wb");
fwrite(&st_dic, sizeof(struct Dictionary), 1, fd);
fclose (fd);
//----------------------------------------------------------------
// The way I need to do it
// Insert the structure into a BLOB column
//----------------------------------------------------------------
conn = mysql_init(NULL);
if (!mysql_real_connect(conn, DB_SERVER, DB_USER, DB_PWD, DB_NAME, 0, NULL, 0))
{
fprintf(stderr, "ERROR:%s\n", mysql_error(conn));
exit (1) ;
}
//....
sprintf (str_query, "INSERT INTO myTables (id, blob_field) VALUES (0, '%s')", &st_dic) ;
//....
if (mysql_query(conn, str_query))
{
fprintf(stderr,"FAIL TO RUN SQL : [%s]\n", str_query) ;
fprintf(stderr, "%s\n", mysql_error(conn));
}
mysql_free_result(res);
mysql_close(conn);
return (0) ;
}
When working with binary objects text protocol (mysql_query/mysql_real_query) is not the best option, since special characters like '\0' are not supported. That means you have to allocate additional buffer (2 * (size of blob) + 1) for transforming the binary object.
Solution 1: mysql_real_escape()
char *buffer = malloc(sizeof(struct Dictionary) * 2 + 1);
mysql_real_escape_string(conn, buffer, &st_dic, sizeof(struct Dictionary));
sprintf(str, "INSERT INTO myTables (id, blob_field) VALUES (0, '%s')", buffer);
if (mysql_query(conn, str))
{
/* Error handling */
}
Solution 2: mysql_hex_string()
char *buffer = malloc(sizeof(struct Dictionary) * 2 + 1);
mysql_hex_string(buffer, &st_dic, sizeof(struct Dictionary));
sprintf(str, "INSERT INTO myTables (id, blob_field) VALUES (0, X'%s')", buffer);
if (mysql_query(conn, str))
{
/* Error handling */
}
Alternative:
A better solution is to use prepared statements which use the binary protocol:
Code without error handling:
MYSQL_BIND bind;
MYSQL_STMT *stmt;
stmt= mysql_stmt_init(conn);
mysql_stmt_prepare(stmt, INSERT INTO myTables (id, blob_field) VALUES (0, ?)", 1);
memset(&bind, 0, sizeof(MYSQL_BIND));
bind.buffer_type= MYSQL_TYPE_BLOB;
bind.buffer= &st_dic;
bind.buffer_length= sizeof(struct Dictionary);
mysql_stmt_bind_param(stmt, &bind);
mysql_stmt_execute(stmt);
I've been tearing my hair out for a while on this one. The C code is called from a bash script, which loops through a command's output in a while loop and passes variables to the C script as args. It goes through a list and partitions data properly. I've been using the C MySQL api, and up until now everything has been relatively straight forward. It tries to run a SELECT(EXISTS) command to dictate whether to input a new row, or update an existing one.
I have typed the command into MySQL terminal and it works perfectly. I have even printf'd it and copied the command directly into the terminal. It works....
So why then, am I getting Syntax errors? I've tried escaping fields and input using backticks, single quotes and double quotes and I'm still getting this dumbounding error. I thought maybe it was something to do with the null space? But I'm at my witts end. Here's the code, any advice would be greatly appreciated :)
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <mysql/mysql.h>
const int MAXLEN = 100;
/* Compile with:
gcc db.connect.c `mysql_config --libs` -O1
for the best results
*/
/* Function definitions for later */
void finish_with_error(MYSQL *con);
int send_query(MYSQL *con, char query[MAXLEN]);
/* If any SQL commands fail, return an error message */
void finish_with_error(MYSQL *con)
{
fprintf(stderr, "%s\n", mysql_error(con));
mysql_close(con);
exit(1);
}
/* Helper function to send queries to MySQL database */
int send_query(MYSQL *con, char query[MAXLEN])
{
if (mysql_query(con, query)) {
finish_with_error(con);
}
return 0;
}
int main(int argc, char ** argv)
{
// Establish MySQL API connection, if not- fail with err
MYSQL *con = mysql_init(NULL);
if (con == NULL) {
finish_with_error(con);
}
// Connection string.
if (mysql_real_connect(con, "localhost", "user", "password",
NULL, 0, NULL, 0) == NULL){
finish_with_error(con);
}
if (argv[1] == NULL){
printf("No query passed, terminating script \n");
return 1;
}
if (argv[1] != NULL) {
if( strcmp( argv[1], "--help" ) == 0 ) {
printf("This program was created to interact with MySQL, by checking and updating live network stats\n");
printf("It has 2 parameters, an IP address to look in the database for and a value to update a field by, \
if that IP address is found. ");
printf("If the value is not found, the program will insert a new row.");
return 1;
}
// Works out how much memory to allocate to buffer for snprintf
// Originally cmd_len was 65- as this was the amount of bits needed by the address string.
// This was changed to MAXLEN to prevent SEGFAULTS and give the function breathing room.
size_t cmd_len = MAXLEN;
size_t param_len = sizeof(argv[2]);
size_t q_len = cmd_len + param_len;
// Allocates that memory to a buffer, referenced as query
char *query = malloc(sizeof(char) * q_len);
snprintf(query, q_len, "SELECT EXISTS(SELECT * FROM `analytics`.`live` WHERE `foreign_addr` = `%s`)", argv[1]);
printf("%s\n", query);
send_query(con, query);
free(query);
// Used to store the result of the MySQL select commands
MYSQL_RES *result = mysql_store_result(con);
if (result == NULL) {
finish_with_error(con);
}
// num_fields stores the number of fields, i and x are counters, answer is 1 or 0
int num_fields = mysql_num_fields(result);
int i = 0;
// Loops through each row in the answer statement.
// There will only be one row in the answer, which will be 1 or 0
// Basically, if the IP is found.
MYSQL_ROW row;
while ((row = mysql_fetch_row(result))){
for (i=0; i<num_fields; i++) {
// If the IP isn't in the table
if(!atoi(row[i]))
send_query(con, argv[1]);
// If the IP is already in the table
if(atoi(row[i])) {
snprintf(query, q_len, "UPDATE analytics.live SET count=count+1 WHERE foreign_addr = '%s'", argv[1]);
printf("%s\n", query);
free(query);
snprintf(query, q_len, "UPDATE analytics.live SET dat_sent = dat_sent + %s", argv[2]);
printf("%s\n", query);
free(query);
}
}
}
mysql_close(con);
return 1;
}
mysql_close(con);
return 0;
}
I don't usually code using C programming language but I learned it in school (so please bear with me because I am still a newbie).
In short, I was recently assigned to write code in C in order to delete rows from a table in MySQL database.
I used stackoverflow and other resources to help me with this code!
This is my code (not all of it):
void delete_rows(MYSQL *con)
{
char selection_query[256];
char deletion_query[256];
sprintf(selection_query, "SELECT id FROM <table> WHERE status = 'PROCESSING'\
AND started < DATE(NOW()) - INTERVAL %d DAY", expire_processing_days);
if (mysql_query(con, selection_query))
{
finish_with_error(con);
}
MYSQL_RES *result = mysql_store_result(con);
if (result == NULL)
{
finish_with_error(con);
}
int num_fields = mysql_num_fields(result);
MYSQL_ROW row;
while ((row = mysql_fetch_row(result)))
{
for(int i = 0; i < num_fields; i++)
{
printf("Deleting process with id: %s ", row[i] ? row[i] : "NULL");
sprintf(deletion_query, "DELETE FROM <table> WHERE id = %d", row[i]);
if (mysql_query(con, deletion_query))
{
finish_with_error(con);
}
mysql_commit(con);
}
printf("\n");
}
mysql_free_result(result);
}
int main()
{
MYSQL *con;
DB_CONN_PARAMS *params = calloc(1,sizeof(DB_CONN_PARAMS));
//just an alternative way of passing connection params, find a struct easier
strcpy(params->host, <host>);
strcpy(params->user, <user>);
strcpy(params->pass, <password>);
strcpy(params->db, <database>);
MYSQL * connect_db(DB_CONN_PARAMS *params);
con = connect_db(params);
//we don't need the struct anymore
free(params);
params = NULL;
//kill processes that are incomplete/hanging
delete_rows(con);
//close mysql connection
mysql_close(con);
return EXIT_SUCCESS;
}
So, the code above compiles and runs without any errors, it prints out the ids of the rows that I want to delete. But when I go to the database to check the rows, they are still there!
Is there anything I am missing?
Ok, I have figured it out finally!
I changed the %d to %s in the following line:
sprintf(deletion_query, "DELETE FROM WHERE id = %d", row[i]);.
Because row[i] is a string, I was blind to that.
I was able to figure it out by printing the whole MySQL command and noticed that the id passed is wrong!
Thank you everyone for your attempts to help me.
I'm trying to build a C-program to add data to my MYSQL database and I would like to use variables within the SQL string. I want to insert UNIX time (epoch) in one column and the result from an energy meter into the other (double)
Even though it builds without errors or warnings I can't get it to insert the data into the table. Can someone give me a hint of where to look?
Thankful for all help I can get as I'm pretty much fumbling in the dark
Regards,
Mikael
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <time.h>
#include <math.h>
#include <mysql.h>
#include <my_global.h>
#include <stdlib.h> // For exit function
int loggingok; // Global var indicating logging on or off
double result = 323.234567; //Debug
double actual_time_sec;
void calculate_watts(void)
{
MYSQL *conn = mysql_init(NULL);
char *server = "localhost";
char *user = "root";
char *password = "password"; /* set me first */
char *database = "power";
char SQL_String[100];
char time_char[11];
char result_char[11];
time_t actual_time;
actual_time = time(0);
actual_time_sec = difftime(actual_time,0);
sprintf(time_char,"%g",actual_time_sec);
sprintf(result_char,"%g",result);
printf("Tid: %g\n",actual_time_sec); //Debug
printf("Resultat: %g\n", result); //Debug
strcpy(SQL_String, "INSERT INTO consumption(time,consumption) VALUES(");
strcat(SQL_String, time_char);
strcat(SQL_String, ",");
strcat(SQL_String, result_char);
strcat(SQL_String, ")");
printf("SQL: %s", SQL_String); //Debug
// SQL_String = "INSERT INTO consumption(time,consumption) VALUES('"+ actual_time_sec +"',"+ result +")";
if (!mysql_real_connect(conn, server, user, password, database, 0, NULL, 0)) {
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1); }
if (mysql_query(conn, SQL_String)) {
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1); }
}
int main (int argc, char *argv[])
{
printf(argv[1]); //Debug
if(strcmp(argv[1], "db")) {
loggingok=1;
printf("Efergy E2 Classic decode \n\n");
calculate_watts(); }
else {
loggingok=0; }
return 0;
}
here is a great example...
http://php.net/mysql_query. Note the usage of sprintf here. The 2nd and 3rd parameters work with the sprintf to place the data in these 2 parameters exactly where they are needed in the SQL statement.
$query = sprintf("SELECT firstname, lastname, address, age FROM friends
WHERE firstname='%s' AND lastname='%s'",
mysql_real_escape_string($firstname),
mysql_real_escape_string($lastname));
// Perform Query
$result = mysql_query($query);
// Check result
// This shows the actual query sent to MySQL, and the error. Useful for debugging.
if (!$result) {
$message = 'Invalid query: ' . mysql_error() . "\n";
$message .= 'Whole query: ' . $query;
die($message);
}
Please note the usage of if (!$result) this allows you to do a quick validation of if you have success or not. If an error is found the text resturned from mysql_error is placed in the message variable and then presented when the app dies.
Is there a way to directly display the content of a query in Mysql using C?
What I mean is:
through mysql shell if I type : SELECT * FROM table_name; I get the query result in a neat and formatted way.
If I want to do the same thing using Api C I have to write several lines of codes and the final result is far from being nice (at least this is my personal experience )
For example :
void display_Table1(MYSQL *conn)
{
int jj,ii;
char query[512];
sprintf(query, "SELECT * FROM Table1 ;");
if (mysql_query (conn, query)) {
printf("\nErrore query:\n");
printf("%s", mysql_error(conn),"\n");
result = mysql_store_result(conn);
if (result) {
num_rows = mysql_num_rows(result);
num_fields =mysql_num_fields(result);
//printf("Number of rows=%u Number of fields=%d \n", num_rows,num_fields);
//printf(" ");
}
else
{
printf("Result set is empty");
}
// Print column headers
fields = mysql_fetch_fields(result);
for(jj=0; jj < num_fields; jj++)
{
printf("\n%s\t\t",fields[jj].name);
}
printf("\n\t ");
// print query results
while(row = mysql_fetch_row(result)) // row pointer in the result set
{
for(ii=0; ii < num_fields; ii++)
{
printf("%s\t", row[ii] ? row[ii] : "NULL"); // Not NULL then print
}
printf("\n");
}
if(result)
{
mysql_free_result(result);
result = NULL;
}
}
}
That's a knotty problem to solve. I get headers one after the other in a vertical way.
I also get
Commands out of sync; you can't run this command now
Firstly, there is no direct way to print out a formatted display. What you can do, is use
MYSQL_FIELD *field = mysql_fetch_field (resultset);
col_len = field->max_length;
if(col_len < strlen(field->name))
col_len = strlen(field->name);
to find out the maximum width of a column, and the space the data accordingly.