SQLite Learning Note 7:c using SQLite's Open database in the language

The basic content of the database is almost the same as before. Take a look at how to use SQLite in the C language.

One interface

Sqlite3_open (const char *filename, Sqlite3 **ppdb)

Open the database, assume that the database does not exist, create a new database, and open

Sqlite3_close (sqlite3*)

Close the database. Assuming that there are no statements running out before closing, you will returnSqlite_busy

Two examples

1 folder structure

projects{

main.c//code is located in the file

sqlite{//Download down the SQLite compressed package files folder after decompression

shell.c//This document is not actually available in the project. This file is used to generate the SQLite command tool, detailed can be taken: SQLite Learning Note 1

Sqlite3.c

Sqlite3.h

Sqlite3ext.h

}

}

2 Source code

// main.c
#include <stdio.h>
#include <stdlib.h>
#include "sqlite/sqlite3.h"

#define DB_NAME "hanfeng.db"

int main()
{
    sqlite3* db = NULL ;
    char* msg = NULL ;
    int ret = 0 ;
    
    ret = sqlite3_open(DB_NAME, &db);
    if (ret){
        fprintf(stderr, "error open datebase:%s\n.", DB_NAME) ;
        exit(0) ;
    }
    else{
        fprintf(stdout, "successfully open datebase.\n") ;
    }
    sqlite3_close(db) ;
    return 0;
}

To facilitate future expansion, code changes such as the following are now available:

#include <stdio.h>
#include <stdlib.h>
#include "sqlite/sqlite3.h"

#define DB_NANE "sqlite/test.db"

sqlite3 *db = NULL;
char* sql = NULL;
char *zErrMsg = NULL;
int ret = 0;

typedef enum{
    false,
    true
} bool;

static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
    int i = 0;
    for(i=0; i < argc; i++){
        printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
    }
    printf("\n");
    
    return 0;
}

bool connectDB()
{
    ret = sqlite3_open(DB_NANE, &db);
    
    if( ret != SQLITE_OK){
        fprintf(stderr, "Error open database: %s\n", sqlite3_errmsg(db));
        sqlite3_free(zErrMsg);
        
        return false;
    }
    
    fprintf(stdout, "Successfully opened database\n");
    return true;
}

bool closeDB()
{
    int ret = 0;
    ret = sqlite3_close(db);
    if ( ret == SQLITE_BUSY ){
        return false;
    }
    
    return true;
}

int main(int argc, char* argv[])
{
    connectDB();
    closeDB();
    
    return 0;
}

3 Compile execution

There are two ways to do this, based on the previous notes. We do not configure the environment for SQLite. But download unzip get column A directory SQLite, so. Need to use such as the following command:

Gcc-o main main.c./SQLITE/SQLITE3.C-LPTHREAD-LDL

Assuming that the download configuration has SQLite installed, you will need to include the above header file instead:

#include <sqlite3.h>

Then run the command:

Gcc-o main MAIN.C  -lsqlite3

After the command is finished, a running file called Main is generated, and the input is:

./main

You can see the results.

#在编译时使用g + + will error: error:invalid conversion from ' const void* ' to ' const char* '

G++ seems to be more demanding on type conversions and does not support this conversion.

Passing heroes, know how to compile with g++, please advise ...

SQLite Learning Note 7:c using SQLite's Open database in the language