I want to update multiple rows like below
update mytable set s_id = {0} where id = {1}
(Here s_id is evaluated based on some complex logic).
For performance reason, updates should happen in batches. Is there any way to batch the update statements and execute the batch through single execute statements? I know in JAVA we can do this through JDBC. Is there similar way in C#?
Thanks in advance
Yes, you can use an SqlDataAdapter.
The SqlDataAdapter has InsertCommand and UpdateCommand properties which allow you to specify an SQLCommand to use to insert new rows into the database and an SqlCommand to update rows in the database respectively.
You can then pass a DataTable to the Update method of the dataadapter, and it will batch up the statements to the server - for rows in the DataTable that are new rows, it executes the INSERT command, for modified rows it executes the UPDATE command.
You can define the batch size using the UpdateBatchSize property.
This approach allows you to deal with large volumes of data, and allows you to nicely handle errors in different ways, i.e. if an error is encountered with a particular update, you can tell it to NOT throw an exception but to carry on with the remaining updates by setting the ContinueUpdateOnError property.
Yes, you can build a plain-text SQL command (parameterized for security), like this:
SqlCommand command = new SqlCommand();
// Set connection, etc.
for(int i=0; i< items.length; i++) {
command.CommandText += string.Format("update mytable set s_id=@s_id{0} where id = @id{0};", i);
command.Parameters.Add("@s_id" + i, items[i].SId);
command.Parameters.Add("@id" + i, items[i].Id);
}
command.ExecuteNonQuery();
Use a StringBuilder (System.Text.StringBuilder) to build your Sql, such as:
StringBuilder sql = new StringBuilder();
int batchSize = 10;
int currentBatchCount = 0;
SqlCommand cmd = null; // The SqlCommand object to use for executing the sql.
for(int i = 0; i < numberOfUpdatesToMake; i++)
{
int sid = 0; // Set the s_id here
int id = 0; // Set id here
sql.AppendFormat("update mytable set s_id = {0} where id = {1}; ", sid, id);
currentBatchCount++;
if (currentBatchCount >= batchSize)
{
cmd.CommandText = sql.ToString();
cmd.ExecuteNonQuery();
sql = new StringBuilder();
currentBatchCount = 0;
}
}
int id = 0 could just as easily change the whole query.
Create a set of those updates (with the id's filled in), separate them by semicolon in one string, set the resulting string to a SqlCommand's CommandText property, then call ExecuteNonQuery().
