sqlite c/c++ 編程接口

1. 安裝

在 c/c++ 程序中使用 sqlite 之前，我們需要確保機器上已經(jīng)有 sqlite 庫?？梢圆榭?sqlite 安裝章節(jié)了解安裝過程。

2. c/c++ 接口 api

以下是重要的 c&c++ / sqlite 接口程序，可以滿足您在 c/c++ 程序中使用 sqlite 數(shù)據(jù)庫的需求。如果您需要了解更多細節(jié)，請查看 sqlite 官方文檔。

3. 連接數(shù)據(jù)庫

下面的 c 代碼段顯示了如何連接到一個現(xiàn)有的數(shù)據(jù)庫。如果數(shù)據(jù)庫不存在，那么它就會被創(chuàng)建，最后將返回一個數(shù)據(jù)庫對象。

#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));
      exit(0);
   }else{
      fprintf(stderr, "opened database successfully\n");
   }
   sqlite3_close(db);
}

現(xiàn)在，讓我們來編譯和運行上面的程序，在當前目錄中創(chuàng)建我們的數(shù)據(jù)庫 test.db。您可以根據(jù)需要改變路徑。

$gcc test.c -l sqlite3
$./a.out
opened database successfully

如果要使用 c++ 源代碼，可以按照下列所示編譯代碼：

$g++ test.c -l sqlite3

在這里，把我們的程序鏈接上 sqlite3 庫，以便向 c 程序提供必要的函數(shù)。這將在您的目錄下創(chuàng)建一個數(shù)據(jù)庫文件 test.db，您將得到如下結(jié)果：

-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

4. 創(chuàng)建表

下面的 c 代碼段將用于在先前創(chuàng)建的數(shù)據(jù)庫中創(chuàng)建一個表：

#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));
      exit(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;
}

上述程序編譯和執(zhí)行時，它會在 test.db 文件中創(chuàng)建 company 表，最終文件列表如下所示：

-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

5. insert 操作

下面的 c 代碼段顯示了如何在上面創(chuàng)建的 company 表中創(chuàng)建記錄：

#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));
      exit(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;
}

上述程序編譯和執(zhí)行時，它會在 company 表中創(chuàng)建給定記錄，并會顯示以下兩行：

opened database successfully
records created successfully

6. select 操作

在我們開始講解獲取記錄的范例之前，讓我們先了解下回調(diào)函數(shù)的一些細節(jié)，這將在我們的范例使用到。這個回調(diào)提供了一個從 select 語句獲得結(jié)果的方式。它聲明如下：

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 */
);

如果上面的回調(diào)在 sqlite_exec() 程序中作為第三個參數(shù)，那么 sqlite 將為 sql 參數(shù)內(nèi)執(zhí)行的每個 select 語句中處理的每個記錄調(diào)用這個回調(diào)函數(shù)。

下面的 c 代碼段顯示了如何從前面創(chuàng)建的 company 表中獲取并顯示記錄：

#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));
      exit(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;
}

上述程序編譯和執(zhí)行時，它會產(chǎn)生以下結(jié)果：

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

7. update 操作

下面的 c 代碼段顯示了如何使用 update 語句來更新任何記錄，然后從 company 表中獲取并顯示更新的記錄：

#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));
      exit(0);
   }else{
      fprintf(stderr, "opened database successfully\n");
   }

   /* 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: %s\n", zerrmsg);
      sqlite3_free(zerrmsg);
   }else{
      fprintf(stdout, "operation done successfully\n");
   }
   sqlite3_close(db);
   return 0;
}

上述程序編譯和執(zhí)行時，它會產(chǎn)生以下結(jié)果：

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

8. delete 操作

下面的 c 代碼段顯示了如何使用 delete 語句刪除任何記錄，然后從 company 表中獲取并顯示剩余的記錄：

#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));
      exit(0);
   }else{
      fprintf(stderr, "opened database successfully\n");
   }

   /* 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: %s\n", zerrmsg);
      sqlite3_free(zerrmsg);
   }else{
      fprintf(stdout, "operation done successfully\n");
   }
   sqlite3_close(db);
   return 0;
}

上述程序編譯和執(zhí)行時，它會產(chǎn)生以下結(jié)果：

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