文章目錄

• SQLite示例教程
• • 使用SQLite創建數據庫
  • 使用SQLite3創建一個數據表
  • 在上述數據表中插入數據
  • 數據的獲取
  • UPDATE操作
  • delate操作

SQLite示例教程

使用SQLite創建數據庫

*sqlite3_open(const char *filename, sqlite3 *ppDb)

如果 filename 參數是 NULL 或 ‘:memory:’，那么 sqlite3_open() 將會在 RAM 中創建一個內存數據庫，這只會在 session 的有效時間內持續。

如果文件名 filename 不為 NULL，那么 sqlite3_open() 將使用這個參數值嘗試打開數據庫文件。如果該名稱的文件不存在，sqlite3_open() 將創建一個新的命名為該名稱的數據庫文件并打開。

簡單的來說就是會打開一個數據庫文件，文件不存在就會創建一個對應名字的數據庫文件

*sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char *errmsg)

在這里，第一個參數 sqlite3 是打開的數據庫對象，sqlite_callback 是一個回調，data 作為其第一個參數，errmsg 將被返回用來獲取程序生成的任何錯誤。

sqlite3_exec() 程序解析并執行由 sql 參數所給的每個命令，直到字符串結束或者遇到錯誤為止

sqlite3_close(sqlite3*)

如果還有查詢沒有完成，sqlite3_close() 將返回 SQLITE_BUSY 禁止關閉的錯誤消息。

#include <stdio.h> #include <stdlib.h> #include <sqlite3.h>int main(int argc, char* argv[]) {sqlite3 *db;char *zErrMsg = 0;int rc;//sqlite3_open 打開指定的數據庫文件，文件不存在就創建一個新的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);return 0; } $ gcc creat_db.c -l sqlite3 $ ./a.out Opened database successfully $ ls a.out creat_db.c test.db

使用SQLite3創建一個數據表

#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 *///< 打開數據庫文件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 *///< 建表語句定義/* 創建主鍵 */ //"ID INT PRIMARY KEY NOT NULL," 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 *///< 返回程序生成的執行的任何返回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; } $ gcc creat_db_datebase.c -l sqlite3 $ ./a.out Opened database successfully Table created successfully

數據庫內筒如下：

在上述數據表中插入數據

#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;/********************第一步，打開數據庫文件，獲取數據庫文件操作句柄*************************/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");}/********************第二步、定義數據操作語句***********************/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 );";/********************第三步、執行建表語句建立數據表**********************/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; } $ ./a.out Opened database successfully Records created successfully

數據的獲取

• 獲取數據中需要用到回調函數的使用

typedef int (*sqlite3_callback)( void*, /* sqlite3_exec() 中第四個參數*/ int, /* 行中的列數 */ char**, /* 行中的字符串 */ char** /* 列名的字符串數組*/ ); #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; } $ gcc creat_db_select.c -l sqlite3 $ ./a.out Opened database successfully Callback function called: ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 20000.0Callback function called: ID = 2 NAME = Allen AGE = 25 ADDRESS = Texas SALARY = 15000.0Callback function called: ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0Callback function called: ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0Operation done successfully

UPDATE操作

#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; }

執行結果

$ gcc creat_db_update.c -l sqlite3 $ ./a.out Opened database successfully Callback function called: ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 25000.0 #原來是 2000Callback function called: ID = 2 NAME = Allen AGE = 25 ADDRESS = Texas SALARY = 15000.0Callback function called: ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0Callback function called: ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0Operation done successfully

delate操作

#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; }

執行結果

$ ./a.out Opened database successfully Callback function called: ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 25000.0Callback function called: ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0Callback function called: ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0Operation done successfully

總結

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