小编Gen*_*Ziy的帖子

将ALTER语句添加到现有列的语句的正确语法是什么？

我可以添加没有错误的新列:

ALTER TABLE tb_TableName ADD Record_Status varchar(20)

但是,如果我尝试使用以下语句更改现有列以应用默认值:

ALTER TABLE tb_TableName 
ALTER COLUMN Record_Status VARCHAR(20) NOT NULL DEFAULT ''

要么

ALTER TABLE tb_TableName 
ALTER Record_Status VARCHAR(20) NOT NULL DEFAULT ''

我收到一个错误:

'Record_Status'附近的语法不正确.

我必须找到列表中是否存在字符串以避免重复插入:以下是来自Microsoft站点的示例:

using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        List<string> dinosaurs = new List<string>();

        dinosaurs.Add("Compsognathus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("Oviraptor");
        dinosaurs.Add("Velociraptor");
        dinosaurs.Add("Deinonychus");
        dinosaurs.Add("Dilophosaurus");
        dinosaurs.Add("Gallimimus");
        dinosaurs.Add("Triceratops");

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\nTrueForAll(EndsWithSaurus): {0}",
            dinosaurs.TrueForAll(EndsWithSaurus));

        Console.WriteLine("\nFind(EndsWithSaurus): {0}", 
            dinosaurs.Find(EndsWithSaurus));

        Console.WriteLine("\nFindLast(EndsWithSaurus): {0}",
            dinosaurs.FindLast(EndsWithSaurus));

        Console.WriteLine("\nFindAll(EndsWithSaurus):");
        List<string> sublist = dinosaurs.FindAll(EndsWithSaurus);

        foreach(string dinosaur in sublist)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine(
            "\n{0} elements removed by RemoveAll(EndsWithSaurus).", 
            dinosaurs.RemoveAll(EndsWithSaurus));

        Console.WriteLine("\nList now contains:");
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\nExists(EndsWithSaurus): {0}", 
            dinosaurs.Exists(EndsWithSaurus));
    }

    // Search predicate …

Base on recommendation from https://msdn.microsoft.com/en-us/library/system.io.path.getrandomfilename(v=vs.110).aspx I have replaced GetTempFileName with GetRandomFileName to get a name for the temp file. And it cause a problem. Sometimes GetRandomFileName return not a file name but location in System32 folder. And of cause users with no admin rights are having an error that file is not found. Do I missed anything?

Here is a code:

string tempFileName = Path.GetRandomFileName(); FileStream tempFileStream = null; tempFileStream = File.Open(tempFileName, FileMode.Create, FileAccess.ReadWrite);

later on when I try …