Database Connectivity using C/C++

In this section, you will learn how to use SQLite in C/C++ programs.
Before you start using SQLite in our C/C++ programs, you need to make sure that you have SQLite library set up on the machine. You can check the SQLite Installation chapter to understand the installation process.
Following are important C/C++ SQLite interface routines, which can suffice your requirement to work with SQLite database from your C/C++ program. If you are looking for a more sophisticated application, then you can look into SQLite official documentation.
sqlite3_open(const char *filename, sqlite3 **ppDb)
sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char **errmsg)
sqlite3_close(sqlite3*)
Following C code segment shows how to connect to an existing database. If the database does not exist, then it will be created and finally a database object will be returned.
#include <stdio.h>
#include <sqlite3.h>
int main(int argc, char* argv[]) {
   sqlite3 *db;
   char *zErrMsg = 0;
   int rc;
   rc = sqlite3_open("test.db", &db);
   if( rc ) {
      fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
      return(0);
   } else {
      fprintf(stderr, "Opened database successfully\n");
   }
   sqlite3_close(db);
}
$gcc test.c -l sqlite3
$./a.out
Opened database successfully
Following C code segment will be used to create a table in the previously created database −
#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
static int callback(void *NotUsed, int argc, char **argv, char **azColName) {
   int i;
   for(i = 0; i<argc; i++) {
      printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
   }
   printf("\n");
   return 0;
}
int main(int argc, char* argv[]) {
   sqlite3 *db;
   char *zErrMsg = 0;
   int rc;
   char *sql;
   /* Open database */
   rc = sqlite3_open("test.db", &db);
   if( rc ) {
      fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
      return(0);
   } else {
      fprintf(stdout, "Opened database successfully\n");
   }
   /* Create SQL statement */
   sql = "CREATE TABLE COMPANY(" \
      "ID INT PRIMARY KEY NOT NULL," \
      "NAME TEXT NOT NULL," \
      "AGE INT NOT NULL," \
      "ADDRESS CHAR(50)," \
      "SALARY REAL );";
   /* Execute SQL statement */
   rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
   if( rc != SQLITE_OK ) {
      fprintf(stderr, "SQL error: %s\n", zErrMsg);
      sqlite3_free(zErrMsg);
   } else {
      fprintf(stdout, "Table created successfully\n");
   }
   sqlite3_close(db);
   return 0;
}
-rwxr-xr-x. 1 root root 9567 May 8 02:31 a.out
-rw-r--r--. 1 root root 1207 May 8 02:31 test.c
-rw-r--r--. 1 root root 3072 May 8 02:31 test.db
Following C code segment shows how you can create records in COMPANY table created in the above example –
#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
static int callback(void *NotUsed, int argc, char **argv, char **azColName) {
   int i;
   for(i = 0; i<argc; i++) {
      printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
   }
   printf("\n");
   return 0;
}
int main(int argc, char* argv[]) {
   sqlite3 *db;
   char *zErrMsg = 0;
   int rc;
   char *sql;
   /* Open database */
   rc = sqlite3_open("test.db", &db);
   if( rc ) {
      fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
      return(0);
   } else {
      fprintf(stderr, "Opened database successfully\n");
   }
   /* Create SQL statement */
   sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " \
      "VALUES (1, 'Paul', 32, 'California', 20000.00 ); " \
      "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " \
      "VALUES (2, 'Allen', 25, 'Texas', 15000.00 ); " \
      "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" \
      "VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );" \
      "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" \
      "VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );";
   /* Execute SQL statement */
   rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
   if( rc != SQLITE_OK ) {
      fprintf(stderr, "SQL error: %s\n", zErrMsg);
      sqlite3_free(zErrMsg);
   } else {
      fprintf(stdout, "Records created successfully\n");
   }
   sqlite3_close(db);
   return 0;
}
Opened database successfully
Records created successfully
Before proceeding with actual example to fetch records, let us look at some detail about the callback function, which we are using in our examples. This callback provides a way to obtain results from SELECT statements. It has the following declaration –
typedef int (*sqlite3_callback)(
   void*, /* Data provided in the 4th argument of sqlite3_exec() */
   int, /* The number of columns in row */
   char**, /* An array of strings representing fields in the row */
   char** /* An array of strings representing column names */
);
If the above callback is provided in sqlite_exec() routine as the third argument, SQLite will call this callback function for each record processed in each SELECT statement executed within the SQL argument.
Following C code segment shows how you can fetch and display records from the COMPANY table created in the above example –
#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
static int callback(void *data, int argc, char **argv, char **azColName) {
   int i;
   fprintf(stderr, "%s: ", (const char*)data);
   for(i = 0; i<argc; i++) {
      printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
   }
   printf("\n");
   return 0;
}
int main(int argc, char* argv[]) {
   sqlite3 *db;
   char *zErrMsg = 0;
   int rc;
   char *sql;
   const char* data = "Callback function called";
   /* Open database */
   rc = sqlite3_open("test.db", &db);
   if( rc ) {
      fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
      return(0);
   } else {
      fprintf(stderr, "Opened database successfully\n");
   }
   /* Create SQL statement */
   sql = "SELECT * from COMPANY";
   /* Execute SQL statement */
   rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);
   if( rc != SQLITE_OK ) {
      fprintf(stderr, "SQL error: %s\n", zErrMsg);
      sqlite3_free(zErrMsg);
   } else {
      fprintf(stdout, "Operation done successfully\n");
   }
   sqlite3_close(db);
   return 0;
}
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 20000.0
Callback function called: ID = 2
NAME = Allen
AGE = 25
ADDRESS = Texas
SALARY = 15000.0
Callback function called: ID = 3
NAME = Teddy
AGE = 23
ADDRESS = Norway
SALARY = 20000.0
Callback function called: ID = 4
NAME = Mark
AGE = 25
ADDRESS = Rich-Mond
SALARY = 65000.0
Operation done successfully