sqlite學習筆記10：C語言中使用sqlite之查詢和更新資料

標籤：sql   database   sqlite   資料庫   linux   

前面說到的 sqlite_exec() 中的第三個參數， SQLite 將為 sql 參數內執行的每個 SELECT 語句中處理的每個記錄調用這個回呼函數。

本節添加了兩個函數，selectFromTable和updateTable.

執行個體程式如下：

#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;const char* data = "Callback function called";/* 改為全域的 */int ret = 0;typedef enum{    false,    true} bool;/*typedef int (*sqlite3_callback)(void*,    Data provided in the 4th argument of sqlite3_exec()int,      The number of columns in rowchar**,   An array of strings representing fields in the rowchar**    An array of strings representing column names);*/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 createTable(){    /* 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 */    ret = sqlite3_exec(db, sql, callback, 0, &zErrMsg);    if( ret != SQLITE_OK ){        fprintf(stderr, "Error SQL: %s\n", zErrMsg);        sqlite3_free(zErrMsg);                return false;    }        fprintf(stdout, "Successfully table created\n");        return true;}bool insertRecords(){    /* 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 */    ret = sqlite3_exec(db, sql, callback, 0, &zErrMsg);    if( ret != SQLITE_OK ){        fprintf(stderr, "SQL error: %s\n", zErrMsg);        sqlite3_free(zErrMsg);        return false;    }        fprintf(stdout, "successfully records created\n");    return true;}

bool selectFromTable()/*新加*/{    /* Create SQL statement */    sql = "SELECT * from COMPANY";        /* Execute SQL statement */    ret = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);    if( ret != SQLITE_OK ){        fprintf(stderr, "Error SQL: %s\n", zErrMsg);        sqlite3_free(zErrMsg);        return false;    }        fprintf(stdout, "successfully operation done\n");        return true;}

bool updateTable()/* 新加 */{    /* Create merged SQL statement */    sql = "UPDATE COMPANY set SALARY = 25000.00 where ID=1; "     "SELECT * from COMPANY";        /* Execute SQL statement */    ret = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);    if( ret != SQLITE_OK ){        fprintf(stderr, "SQL error: %s\n", zErrMsg);        sqlite3_free(zErrMsg);                return false;    }        fprintf(stdout, "Successfully operation done \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();    /*createTable();*/    /*insertRecords();*/    selectFromTable();    updateTable();    selectFromTable();    closeDB();        return 0;}