Question

getName_as_Rows是一个包含一些名称的数组。

如果在数据库中找到记录，我想将int值设置为1。

for(int i = 0; i<100; i++)    
{

    using (var command = new SqlCommand("select some column from some table where column = @Value", con1))
    {
        command.Parameters.AddWithValue("@Value", getName_as_Rows[i]); 
        con1.Open();
        command.ExecuteNonQuery();
    }
}

我正在寻找：

bool recordexist;

if the above record exist then bool = 1 else 0 with in the loop.

如果记录存在，如果必须做其他事情。

Answer 1

为了避免对数据库进行N次查询，这在处理，网络等方面可能非常昂贵，我建议你只使用我学到的技巧加入一次。首先，您需要在数据库中使用一个将字符串拆分为表的函数。

CREATE FUNCTION [DelimitedSplit8K]
--===== Define I/O parameters
        (@pString VARCHAR(8000), @pDelimiter CHAR(1))
RETURNS TABLE WITH SCHEMABINDING AS
 RETURN
--===== "Inline" CTE Driven "Tally Table" produces values from 0 up to 10,000...
     -- enough to cover VARCHAR(8000)
  WITH E1(N) AS (
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL 
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL 
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
                ),                          --10E+1 or 10 rows
       E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
       E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
 cteTally(N) AS (--==== This provides the "zero base" and limits the number of rows right up front
                     -- for both a performance gain and prevention of accidental "overruns"
                 SELECT 0 UNION ALL
                 SELECT TOP (DATALENGTH(ISNULL(@pString,1))) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
                ),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                 SELECT t.N+1
                   FROM cteTally t
                  WHERE (SUBSTRING(@pString,t.N,1) = @pDelimiter OR t.N = 0) 
                )
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
 SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY s.N1),
        Item       = SUBSTRING(@pString,s.N1,ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1,8000))
   FROM cteStart s
GO

其次，将100个变量连接成1个字符串：

“Value1”，“Value 2”，“Value 3”....

在Sql Server中，您只需将值与表

连接即可

SELECT somecolumn FROM sometable t
INNER JOIN [DelimitedSplit8K](@DelimitedString, ',') v ON v.Item = t.somecolumn

因此，您一次只能找到100个字符串，只有1个查询。

Answer 2

使用var result = command.ExecuteScalar()并检查是否result != null

但是比循环更好的选择是使用像

这样的选择语句

SELECT COUNT(*) FROM TABLE WHERE COLUMNVAL >= 0 AND COLUMNVAL < 100,

并在其上运行ExecuteScalar，如果值为＆gt; 0，然后将变量设置为1。

如果数据库C＃Sql Query中存在记录，如何将整数值设置为1

2 个答案: