Suppose you have an existing table with multiple columns. There are specific columns in this table that are not relevant now. You do not require these columns.
For example, consider a product table, and in this table, you have a column []. We implemented a separate mechanism to capture product feedback, and this column is not relevant now. Below is my table structure and we need to remove column having data type varchar This table contains 4 million rows, and the user executed the command to select all records from this table.
In another query window, execute the query without the [Productfeedback] column and capture the similar statistics. You can notice that query without the [Productfeedback] column provides improved performance. You see low values of compiled memory, CPU time, reduced wait counts. The query optimizer and SQL database engine require to put an additional effort for this column while it is not useful to retrieve data from it.
Similarly, compare the client statistics of both queries. You can note a significant reduction in the TDS packets received from the server. Bytes sent to the client, Bytes received from the server, client processing time and total processing time for the query that does not contain the [Productfeedback] column.
It can help you to save the network bandwidth as well. Here, I intend that you should perform database clean up and remove the unwanted columns to improve query performance as well.
Connect to an instance in SSMS, expand databases. In the particular database, locate the particular table and expand the columns. It shows all the columns of the particular table. Right-click on the column we want to remove and click on Delete as shown in the following image. It opens a window and lists the column name to remove. The management studio allows us to drop columns from the table in the following ways:.
Step 2: Select the desired table from which we want to delete columns, right-click on it, and select the Design option from the context menu. Step 3: Once we select the Design option, we will see the table in design mode like the below image. Step 4: Right-click the column that we are going to delete and select the Delete Column option from the menu. Step 5: If you get a prompt message to confirm your column's deletion and relationships, click the Yes button. Step 4: Right-click on the column name you want to remove and choose the Delete option.
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Interview Questions. Company Questions. Artificial Intelligence. Cloud Computing. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 12 years, 7 months ago. Active 8 months ago. Viewed 73k times. How do I delete a column from an existing table? Improve this question. Tony L. Roshan Roshan 1 1 gold badge 9 9 silver badges 12 12 bronze badges. Actually, the other question was written 2 years after this one so that would be the duplicate.
Must be a more google friendly title or something. As such I voted to close this question. Add a comment. Active Oldest Votes. The command you're looking for is: alter table tblName drop column columnName where tblName is the name of the table and columnName is the name of the column, but there's a few things you may need to do first. If there are any foreign key references to the column, you'll need to get rid of them first.
If there's an index using that column, you'll need to either get rid of it or adjust it to not use that column. Improve this answer.
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