Question

我正在从数据库中删除记录。它工作正常。但是当数据库中没有数据时它会崩溃。代码在下面给出

 int noOfRecordsDeleted;

     [self openDatabaseConnection];

    //  query = [NSString stringWithFormat:@"delete from %@ where %@",query];
    NSLog(@"del query=%@",query);
    const char *sql = [query cStringUsingEncoding:NSUTF8StringEncoding];
    sqlite3_stmt *statement = nil;

    if(sqlite3_prepare_v2(dataBaseConnection,sql, -1, &statement, NULL)!= SQLITE_OK)
    {   
                                   NSAssert1(0,@"error preparing statement",sqlite3_errmsg(dataBaseConnection));
    }



    else
    {
        int success = sqlite3_step(statement);
        NSLog(@"%d",success);
    }
    sqlite3_finalize(statement);
      noOfRecordsDeleted = sqlite3_changes(dataBaseConnection);
   [self closeDatabaseConnection];
    return noOfRecordsDeleted;

工作正常。但是，如果我在数据库中添加数据，那么它就会崩溃

[self openDatabaseConnection];

NSString *query;

query = [NSString stringWithFormat:@"insert into Userdetail(aboutMe,anniversary,areacode,birthdate,device_id,chat_id,emailid,gender   ,image,last_login,latitute,longitude,Looking_For,mobilenumber,mobilenumber1          ,mobilenumber2,mood,name,password,place,profileviews,statusmessage) values ('%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@','%@')",aboutMe,anniversarydate,areacode,birthdate,
    device_id,chat_id,email_id,gender,image,last_login,latitude,longitude,looking_for,mobilenumber,mobilenumber1,mobilenumber2,mood,name,password,place,profileviews,statusmessage];

NSLog(@"saveNewTemplateData query=%@",query);
const char *sql = [query cStringUsingEncoding:NSUTF8StringEncoding];
sqlite3_stmt *statement = nil;if(sqlite3_prepare_v2(dataBaseConnection,sql , -1, &statement, NULL)!= SQLITE_OK)
{
    NSAssert1(0,@"error preparing statement",sqlite3_errmsg(dataBaseConnection));
}
else
{
    sqlite3_step(statement);
}
sqlite3_finalize(statement);
[self closeDatabaseConnection];

以上是代码

Answer 1

首先使用以下语句检查数据库是否为空

if(sqlite3_column_text(statement, 0) != nil){//Data exists}

然后在if方法中添加代码以删除dataBase。它工作正常。

Answer 2

query = [NSString stringWithFormat:@"delete from %@ where %@",query];

这个查询意味着什么我认为你的查询错误请仔细检查

如果错误以编程方式持续检查使用if(sqlite3_column_text(statement, 0) != nil)

Answer 3

if (condition for check database empty (select * from table)){

}else{

//Perform Delete operation

}

Answer 4

我发现有一个问题是，无论状态为sqlite3_finalize(statement);，您都在调用sqlite3_prepare_v2。如果sqlite3_finalize成功执行，您只需致电sqlite3_prepare_v2。

将其更改为：

if(sqlite3_prepare_v2(dataBaseConnection,sql, -1, &statement, NULL)!= SQLITE_OK)
{   
    NSAssert1(0,@"error preparing statement",sqlite3_errmsg(dataBaseConnection));
}
else
{
    int success = sqlite3_step(statement);
    NSLog(@"%d",success);
    sqlite3_finalize(statement);
}

从sqlite中的空数据库中删除

4 个答案: