SQLite – C/C++

f(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 successfullySELECT 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 successfullyUPDATE 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 successfullyDELETE 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, call