SQLite - C/C++

安装

在 C/C++ 程序中使用 SQLite 之前，我们需要确保机器上已经有 SQLite 库。可以查看 SQLite 安装章节了解安装过程。

C/C++ 接口 API

以下是重要的 C&C++ / SQLite 接口程序，可以满足您在 C/C++ 程序中使用 SQLite 数据库的需求。如果您需要了解更多细节，请查看 SQLite 官方文档。

连接数据库

下面的 C 代码段显示了如何连接到一个现有的数据库。如果数据库不存在，那么它就会被创建，最后将返回一个数据库对象。

#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);}

现在，让我们来编译和运行上面的程序，在当前目录中创建我们的数据库 test.db。您可以根据需要改变路径。

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

如果要使用 C++ 源代码，可以按照下列所示编译代码：

$g++ test.c -l sqlite3

在这里，把我们的程序链接上 sqlite3 库，以便向 C 程序提供必要的函数。这将在您的目录下创建一个数据库文件 test.db，您将得到如下结果：

-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

创建表

下面的 C 代码段将用于在先前创建的数据库中创建一个表：

#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;}

上述程序编译和执行时，它会在 test.db 文件中创建 COMPANY 表，最终文件列表如下所示：

-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

INSERT 操作

下面的 C 代码段显示了如何在上面创建的 COMPANY 表中创建记录：

#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;}

上述程序编译和执行时，它会在 COMPANY 表中创建给定记录，并会显示以下两行：

Opened database successfullyRecords created successfully

SELECT 操作

在我们开始讲解获取记录的实例之前，让我们先了解下回调函数的一些细节，这将在我们的实例使用到。这个回调提供了一个从 SELECT 语句获得结果的方式。它声明如下：

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 */);

如果上面的回调在 sqlite_exec() 程序中作为第三个参数，那么 SQLite 将为 SQL 参数内执行的每个 SELECT 语句中处理的每个记录调用这个回调函数。

下面的 C 代码段显示了如何从前面创建的 COMPANY 表中获取并显示记录：

#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;}

上述程序编译和执行时，它会产生以下结果：

Opened database successfullyCallback function called: ID = 1NAME = PaulAGE = 32ADDRESS = CaliforniaSALARY = 20000.0Callback function called: ID = 2NAME = AllenAGE = 25ADDRESS = TexasSALARY = 15000.0Callback function called: ID = 3NAME = TeddyAGE = 23ADDRESS = NorwaySALARY = 20000.0Callback function called: ID = 4NAME = MarkAGE = 25ADDRESS = Rich-MondSALARY = 65000.0Operation done successfully

UPDATE 操作

下面的 C 代码段显示了如何使用 UPDATE 语句来更新任何记录，然后从 COMPANY 表中获取并显示更新的记录：

#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;}

上述程序编译和执行时，它会产生以下结果：

Opened database successfullyCallback function called: ID = 1NAME = PaulAGE = 32ADDRESS = CaliforniaSALARY = 25000.0Callback function called: ID = 2NAME = AllenAGE = 25ADDRESS = TexasSALARY = 15000.0Callback function called: ID = 3NAME = TeddyAGE = 23ADDRESS = NorwaySALARY = 20000.0Callback function called: ID = 4NAME = MarkAGE = 25ADDRESS = Rich-MondSALARY = 65000.0Operation done successfully

DELETE 操作

下面的 C 代码段显示了如何使用 DELETE 语句删除任何记录，然后从 COMPANY 表中获取并显示剩余的记录：

#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;}

上述程序编译和执行时，它会产生以下结果：

Opened database successfullyCallback function called: ID = 1NAME = PaulAGE = 32ADDRESS = CaliforniaSALARY = 20000.0Callback function called: ID = 3NAME = TeddyAGE = 23ADDRESS = NorwaySALARY = 20000.0Callback function called: ID = 4NAME = MarkAGE = 25ADDRESS = Rich-MondSALARY = 65000.0Operation done successfully