Efficiently Finding Unique Values In A Database Table?
Feb 11, 2010
I've got a database table with a very large amount of rows. This table represents messages that are logged by a system. Each message has a message type and this is stored it it's own field in the table. I'm writing a website for querying this message log. If I want to search by message type then ideally I would want to have a drop down box listing the message types that have come up in the database. Message types may change over time so I can't hard code the types into the drop down. I'll have to do some sort of lookup. Iterating over the entire table contents to find unique message values is obviously very stupid however being stupid in the database field I'm here asking for a better way. Perhaps a separate lookup table which the database occasionally updates listing just the unique message types that I can populate my drop down from would be a better idea.
The platform I'm using is ASP.NET MVC and SQL Server 2005
In my web application I am working with files. Some files are very large. I use Response.Write() to write the file to the browser. This goes well for the smaller files, but for large files this can take a while and the bandwidth is fully used.
Is it possible to split large documents and send it piece by piece to the browser? Are there other ways to send the document quicker to the browser?I hold the document as a property of an object.
I have a ASP:DropDown list which is populated by the following:
public void Fill1() { string connectionString = WebConfigurationManager.ConnectionStrings["CRM2Sage"].ConnectionString; using (SqlConnection _con = new SqlConnection(connectionString)) using (SqlCommand cmd = new SqlCommand("SELECT * FROM Products", _con)) {
I am stuck with an issue. I have around 200 rows in a table with a particular database. I want to copy those values to another table in a different database.
List<string> ls1 = new List<string>(); Now fill in the cycle with some values: while (...){ lst1.Add (value); )
And when I successfully filled the List, as now reads these values, so that I can save the database?I want all values from List, get into the database, a table, how to do it?
I have data entry form like...There are some empty rows and some of them have values. User can Update existing values and can also fill value in empty rows.I need to map these values in my DB table and some of them will be inserted as new rows into the database and existing record will be updated.I need your suggestions, How can I accomplish this scenario with best approach.
I'm having a gridview in my aspx page with checkbox, User can select one or more than one record(s) at a time and clicks on delete button, Then i'm constructing an object of my DTO and adding all the checked row's Primary Key (DataKeyNames - GUID's in case) to a serializable class and generating an XML and sending it as parameter to the Stored Procedure.
My Doubt is, can i bulk delete all the rows from database table those are present in my XML document??
If it works, I can do bulk update with XML only, i already did bulk insertion by generating an XML..
My Another Question is, Will it affect the performance? Each time when i construct an DTO object and adding it to the Generic List??
WHich one is better, I mean ObjectDataSource or SQLDataSource or my XML method?
I want to compare username and password store in database table to the textbox values for that I am using session variable. How to use dataset for session variable?
How to retrive values from database table using dataset?
I need to loop through an XML document (no problem over there) and check if a value that i find is already in a (a) tag in a div in my XSL document that i am generating, only if the value is not in that (a) tag i should create a new (a) tag for it and put in in the div that i am checking... how to do it dynamically in XSLT?
I know this is a newbie question but, alas , that's what I am. How do I keep values in specifc sql server table unique, in other words how do I prevent any duplicates happening upon creating (inserting) a new table row?
To start with - I'm using VS 2008/.NET 3.5 and working in a company-provided template that leaves me restricted to some/many settings that go beyond the body of the page itself. That said, I need to create a page that will display data from individual cells in a database table that, when lined up would look like a normal sentence. Based on certain criteria I would have certain sections of the sentences hide (ex. if it contains a key phrase or if it's empty).
I've seen a method in which Labels could be used to achieve this effect, where I would assign it the grid coordinates of the cell in a table, but I could never get it to work. I've been successfully connected to the table (LINQDataSource) but still have a blank canvas without this fundamental display technique as that will be all that's in it.
I am returning a dataset from a method and trying to set one of the columns as Primary Key.
CategoryList.Tables[0].PrimaryKey = new DataColumn[] { CategoryList.Tables[0].Columns["CategoryNodeId"] };
Interestingly it gives me this error at run-time, These columns don't currently have unique values.
Now I perfectly know why this error should error, but there are no duplicate keys in this data column. I broke the code in between and bound the dataset to gridview to check if this column contains any duplicates and this is not the case. Here is the result set underneath. Have a look at the first column 'CategoryNodeId'.
CategoryNodeId CategoryId Name ParentCategoryNodeId [code]...
I'll try to make this concise. Anyways, I'm trying to only allow unique data to my database. my database. What I did before adding the entry is to use a Search Query for the value of the txtbox
"SELECT IDnum WHERE IDnum = '" & txtID & "'"
Then compare it with that of the txtbox.
IF objReader("IDNum") <> txtID.textbox then add the entry Else Display a Warning.
in the above code, I can detect the when the user entered an existing value. however, If the user entered a NEW (unique) value an error is Raised "Invalid attempt to read when no data is present" I hit the wall with this.So what I did, Since I can detect Duplicates and have errors when entering unique value, I used the
ON ERROR GOTO statement: I did it like this.
On Error Goto errHandler
If objReader("IDNum") = txtID.textbox then lbl1.text = "Existing Record" objReader.close() [code]....
The Code does what I need but its kinda long, I bet there is an elegant way to do this.
I want to name the headers of the ListView control acording to values of the first rows of a table in the database. This I want to do because the number of columns varies for each cutstomer and also the name of the column.
How does System.Guid.NewGuid() know that the values it generates are unique, for example when i use in a loop?Does it internally store data somewhere? .
I need a way to create unique values for a property in my custom server control..
In this case I will have the poroperty called "Name" and I neeed the value of Name to be unique for each "instance" of the control...
So for instance if I have a page with more then one instance of the control, I dont want the value of the Name property for these instances to be allowed to be the same..
...to put it kind of simple, if I dont remember this incorrect, I want it to be sort of like the ID property..but with another name then ID.
This is my UserRoleList.aspx.cs Code where i am passing the session variable to the page Default.aspx.cs..
And the error is: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. I have gone through many pages , and tried by making the AllowDbNull property making True and then different things.
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using System.Data;
[code]...
This is the code of the second page Default.aspx.cs where i have to user the session varaible to pass in the SQL fucntion named GetDataByUserId as shown below:
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls;
