YouTipSqlite C Cpp
# SQLite – C/C++
## Installation
Before using SQLite in a C/C++ program, we need to ensure that the SQLite library is already present on the machine. You can refer to the SQLite installation section for the installation process.
## C/C++ Interface API
The following are important C/C++ / SQLite interface routines that can meet your needs for using the SQLite database in C/C++ programs. If you need more details, please check the official SQLite documentation.
| Serial Number | API & Description |
| --- | --- |
| 1 | **sqlite3_open(const char *filename, sqlite3 **ppDb)** This routine opens a connection to an SQLite database file and returns a database connection object to be used by other SQLite routines. If the _filename_ parameter is NULL or ':memory:', then sqlite3_open() will create an in-memory database in RAM that will only exist for the duration of the session. If the filename is not NULL, then sqlite3_open() will use this parameter value to try to open the database file. If the file with that name does not exist, sqlite3_open() will create a new database file with that name and open it. |
| 2 | **sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char **errmsg)** This routine provides a shortcut for executing SQL commands provided by the sql parameter, which can consist of multiple SQL commands. Here, the first parameter _sqlite3_ is the opened database object, _sqlite_callback_ is a callback, _data_ is passed as its first argument, and errmsg will be returned to get any error messages generated by the program. The sqlite3_exec() routine parses and executes each command given by the **sql** parameter until the string ends or an error occurs. |
| 3 | **sqlite3_close(sqlite3*)** This routine closes a database connection previously opened by sqlite3_open(). All associated statements should be completed before closing the connection. If there are still queries that haven't been completed, sqlite3_close() will return an SQLITE_BUSY error message prohibiting closure. |
## Connecting to a Database
The following C code segment shows how to connect to an existing database. If the database does not exist, it will be created, and finally, a database object will be returned.
```c
#include
#include
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: %sn", sqlite3_errmsg(db));
exit(0);
}else{
fprintf(stderr, "Opened database successfullyn");
}
sqlite3_close(db);
}
Now, let's compile and run the above program to create our database **test.db** in the current directory. You can change the path as needed.
```bash
$gcc test.c -l sqlite3
$./a.out
Opened database successfully
If you want to use C++ source code, you can compile the code as shown below:
```bash
$g++ test.c -l sqlite3
Here, we link our program with the sqlite3 library to provide the necessary functions to the C program. This will create a database file test.db in your directory, and you will get the following result:
```bash
-rwxr-xr-x. 1 root root 7383 May 8 02:06 a.out
-rw-r--r--. 1 root root 323 May 8 02:05 test.c
-rw-r--r--. 1 root root 0 May 8 02:06 test.db
## Creating a Table
The following C code segment will be used to create a table in the previously created database:
```c
#include
#include
#include
static int callback(void *NotUsed, int argc, char **argv, char **azColName){
int i;
for(i=0; i<argc; i++){
printf("%s = %sn", azColName, argv ? argv : "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: %sn", sqlite3_errmsg(db));
exit(0);
}else{
fprintf(stdout, "Opened database successfullyn");
}
/* 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: %sn", zErrMsg);
sqlite3_free(zErrMsg);
}else{
fprintf(stdout, "Table created successfullyn");
}
sqlite3_close(db);
return 0;
}
When the above program is compiled and executed, it will create the COMPANY table in the test.db file, and the final file list will be as follows:
```bash
-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
## INSERT Operation
The following C code segment shows how to create records in the COMPANY table created above:
```c
#include
#include
#include
static int callback(void *NotUsed, int argc, char **argv, char **azColName){
int i;
for(i=0; i<argc; i++){
printf("%s = %sn", azColName, argv ? argv : "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: %sn", sqlite3_errmsg(db));
exit(0);
}else{
fprintf(stderr, "Opened database successfullyn");
}
/* 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: %sn", zErrMsg);
sqlite3_free(zErrMsg);
}else{
fprintf(stdout, "Records created successfullyn");
}
sqlite3_close(db);
return 0;
}
When the above program is compiled and executed, it will create the given records in the COMPANY table and will display the following two lines:
```bash
Opened database successfully
Records created successfully
## SELECT Operation
Before we start with the examples of fetching records, let's understand some details about the callback function, which will be used in our examples. This callback provides a way to get results from a SELECT statement. It is declared as follows:
```c
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 passed as the third argument to the sqlite_exec() routine, then SQLite will call this callback function for each record processed in each SELECT statement executed within the SQL argument.
The following C code segment shows how to fetch and display records from the COMPANY table created above:
```c
#include
#include
#include
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 = %sn", azColName, argv ? argv : "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: %sn", sqlite3_errmsg(db));
exit(0);
}else{
fprintf(stderr, "Opened database successfullyn");
}
/* 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: %sn", zErrMsg);
sqlite3_free(zErrMsg);
}else{
fprintf(stdout, "Operation done successfullyn");
}
sqlite3_close(db);
return 0;
}
When the above program is compiled and executed, it will produce the following result:
```bash
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
## UPDATE Operation
The following C code segment shows how to use the UPDATE statement to update any record and then fetch and display the updated records from the COMPANY table:
```c
#include
#include
#include
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 = %sn", azColName, argv ? argv : "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: %sn", sqlite3_errmsg(db));
exit(0);
}else{
fprintf(stderr, "Opened database successfullyn");
}
/* Create merged SQL statement */
sql = "UPDATE COMPANY set SALARY = 25000.00 where ID=1; "
"SELECT * from COMPANY";
/* Execute SQL statement */
rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);
if( rc != SQLITE_OK ){
fprintf(stderr, "SQL error: %sn", zErrMsg);
sqlite3_free(zErrMsg);
}else{
fprintf(stdout, "Operation done successfullyn");
}
sqlite3_close(db);
return 0;
}
When the above program is compiled and executed, it will produce the following result:
```bash
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 25000.0
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
## DELETE Operation
The following C code segment shows how to use the DELETE statement to delete any record and then fetch and display the remaining records from the COMPANY table:
```c
#include
#include
#include
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 = %sn", azColName, argv ? argv : "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: %sn", sqlite3_errmsg(db));
exit(0);
}else{
fprintf(stderr, "Opened database successfullyn");
}
/* Create merged SQL statement */
sql = "DELETE from COMPANY where ID=2; "
"SELECT * from COMPANY";
/* Execute SQL statement */
rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);
if( rc != SQLITE_OK ){
fprintf(stderr, "SQL error: %sn", zErrMsg);
sqlite3_free(zErrMsg);
}else{
fprintf(stdout, "Operation done successfullyn");
}
sqlite3_close(db);
return 0;
}
When the above program is compiled and executed, it will produce the following result:
```bash
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 20000.0
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