sqlite学习笔记10：C语言中使用sqlite之查询和更新数据

前面说到的 sqlite_exec() 中的第三个參数， SQLite 将为 sql 參数内运行的每一个 SELECT 语句中处理的每一个记录调用这个回调函数。

本节加入了两个函数。selectFromTable和updateTable.

实例程序例如以下：

#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";/* 改为全局的 */
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 row
char**,   An array of strings representing fields in the row
char**    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;
}