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() 中的第三个参数， 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。

本节添加了两个函数，selectFromTable和updateTable.

实例程序如下：

#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 = %sn",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: %sn",sqlite3_errmsg(db));
        sqlite3_free(zErrMsg);
        
        return false;
    }
    
    fprintf(stdout,"Successfully opened databasen");
    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,&zErrMsg);
    if( ret != SQLITE_OK ){
        fprintf(stderr,"Error SQL: %sn",zErrMsg);
        sqlite3_free(zErrMsg);
        
        return false;
    }
    
    fprintf(stdout,"Successfully table createdn");
    
    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,SALARY) "  
    "VALUES (2,'Allen',25,'Texas',15000.00 ); "     
    "INSERT INTO COMPANY (ID,SALARY)" 
    "VALUES (3,'Teddy',23,'Norway',20000.00 );" 
    "INSERT INTO COMPANY (ID,SALARY)" 
    "VALUES (4,'Mark','Rich-Mond ',65000.00 );";
    
    /* Execute SQL statement */
    ret = sqlite3_exec(db,"SQL error: %sn",zErrMsg);
        sqlite3_free(zErrMsg);
        return false;
    }
    
    fprintf(stdout,"successfully records createdn");

    return true;
}

bool selectFromTable()/*新加*/
{
    /* Create SQL statement */
    sql = "SELECT * from COMPANY";
    
    /* Execute SQL statement */
    ret = sqlite3_exec(db,(void*)data,"successfully operation donen");
    
    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,&zErrMsg);
  if( ret != SQLITE_OK ){
    fprintf(stderr,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;
}

（编辑：李大同）

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