替换SQL中出现的表名

Question

its not first occurence. after a index i need to get the first occurence. the question which you are pointing to is the first occurence without index

i have a sql query which i am trying to modify using String.Replace but my code is replacing where ever it finds brands, how to avoid this

string tempString = 
  "Select t0.brandid,t0.cold,t0.colm, from brands t0 where brandid=@value";

I want to replace brands which is table name between from and before t0 to tempbrands

    int tempindex1 = tempString.IndexOf("FROM ");
string tempString1 = tempString.Replace("brands", "tempbrands ");

expected result is Select t0.brandid,t0.cold,t0.colm, from tempbrands t0 where brandid=@value

Answer 1

Using the previous linked duplicate, i've modified it to specify where to start the search from. I don't know if this is what you were looking for:

string ReplaceFirst(string text, string search, string replace, string from)
{
     int posFrom= text.ToLower().IndexOf(from.ToLower());
     if (posFrom < 0)
     {
          return text;
     }
     int pos = text.ToLower().IndexOf(search.ToLower(),posFrom);
     if (pos < 0)
     {
          return text;
     }
     return text.Substring(0, pos) + replace + text.Substring(pos + search.Length);
}

Usage:

string tempString1 = ReplaceFirst(tempString, "brands", "tempbrands ", "FROM");

Edit

To replace the string between two strings you may modify the previous method like the following, but note the using just a letter as a limit is not possible. For example, i you use "t" as a limit as you ask in the comment, if the table name contains a "t" it's not going to work. You'd rather use "t0":

string ReplaceFirst(string text, string search, string replace, string from, string to)
{

    int posFrom = text.ToLower().IndexOf(from.ToLower());
    if (posFrom < 0)
    {
        return text;
    }
    int posTo = text.ToLower().IndexOf(to.ToLower(),posFrom);
    if (posTo < 0)
    {
        return text;
    }

    int pos = text.ToLower().IndexOf(search.ToLower(), posFrom);
    if (pos < 0 ||pos >posTo)
    {
        return text;
    }
    return text.Substring(0, pos) + replace + text.Substring(pos + search.Length);
}

Usage:

string tempString1 = ReplaceFirst(tempString, "brands", "tempbrands ", "FROM","t0");

Answer 2

I doubt that you want to change the 1st occurence only; it's more likely that you want to rename table within SQL. eg for ( brands => tempbrands change):

  select b1.brandId,
         b2.brandId
    from brands b1, -- both tables should be changed: this
         brands b2  -- ... and this 
   where b1.brandId > b2.brandId and
         b1.colm = b2.colm

you may mant change table names within, say, select as well

  select brands.brandId -- <- all these three occurences should be changed: this,
         brands.colm    --  ... this
    from brands         --  ... and this

A partial solution (complete solution for arbitrary query wants SQL parser ) can be implemented by regular expression :

  String tempString = 
    "Select t0.brandid,t0.cold,t0.colm, from brands t0 where brandid=@value";

  // let's change just whole words "brands" into "tempbrands"
  String sql = Regex.Replace(tempString, 
                             @"\bbrands\b", 
                             match => "tempbrands",
                             RegexOptions.IgnoreCase);

Why the solution is only a partial one? SQL is reacher language than is's usually expected:

  select /*this brands should be left intact*/
         MyField as 'another brands should be spared',
    from "this strange brands table should be skipped"

Answer 3

Make it simply..

string tempString = 
  "Select t0.brandid,t0.cold,t0.colm, from brands t0 where brandid=@value";
tempString = tempString.Replace("from brands", "tempbrands");