rfReplaceAll：全部替换
rfIgnoreCase：忽略大小写

For Example：

var
aStr: String;
begin
aStr := 'This is a book, not a pen!';
ShowMessage(StringReplace (aStr, 'a', 'two', []));//This is two book, not a pen!只替换了第一个符合的字
ShowMessage(StringReplace (aStr, 'a', 'two', [rfReplaceAll]));//This is two book, not two pen!替换了所有符合的字
aStr := 'This is a book, not A pen!';
ShowMessage(StringReplace (aStr, 'a', 'two', [rfReplaceAll]));//This is two book, not A pen!只替换了符合的字(小写a)
ShowMessage(StringReplace (aStr, 'a', 'two', [rfReplaceAll, rfIgnoreCase]));//This is two book, not two pen!不管大小写替换了所有符合的字
end;

如何读取dbgrid的第i行数据？

query1.close;
query1.sql.text:='select * from yourtable';
query1.open;

dbgrid的总行数就是
query1.recordcount

dbgrid1.Columns.Grid.Fields[7].Value
这个是选中列第八行的值