Monthly Archives: May 2010

Dropping a Column from a table using T-SQL – SQL Server

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This blog explains how to drop a column from a table using T-SQL query. It might be easy to do it from SSMS, on the other side, it is not always convenient to do it from SSMS. When you have to repeat the task of dropping additional columns at a later time, you will have to go back to the object explorer repeatedly and choose those column to be dropped, where as using T-SQL query you just need to change the column name to be dropped. Now let’s look at the script to do it.

ALTER TABLE EmployeeTable DROP COLUMN Gender 
Go

The Syntax to drop a table column is quite simple, it goes this way “ALTER TABLE YOURTABLENAME DROP COLUMN YOURCOLUMN“.

To use the code in this example, first you will need to create the table EmployeeTable using the script in another blog Creating Primary Key in a SQL Server table

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–Bru Medishetty

Creating Primary Key in a SQL Server table

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In this blog we shall learn how to create a Primary Key on a table using T-SQL.

A Primary Key on a table can be either created at the time of creating the table or after the table is created by altering the table and adding the Primary Key Constraint.  This blog covers the first method of creating the table and Primary Key at the same time. The important change in the create table script is to include a section inside the table schema definition by mentioning the keyword CONTRAINT followed by the Primary Key Name followed by the Key words PRIMARY KEY.   

CREATE TABLE EmployeeTable ( EmployeeID INT , FName VARCHAR (25)
, LName VARCHAR (25), Gender VARCHAR (1),
CONSTRAINT [PK_EMP_EMPID] PRIMARY KEY
( EmployeeID ASC ) ) ON [PRIMARY]  GO

Some points to remember about Primary Keys

  • A table can consist of one and only one Primary Key.
  • By default a clustered Primary Key is created.
  • A Primary Key on a table can be based on one or more columns of that table.
  • A Primary Key ensure no duplicate values can exist in that column(s).
  • A Primary Key on one column can be used as a parent key on another table and helps in ensuring referential integrity between those tables.
  • A Primary Key is required when creating a Transactional Publication in Replication

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–Bru Medishetty

SQL Server fails to Start-Troubleshooting the failure

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Many times I see people asking in forums about SQL Server not started and how to troubleshoot the reasons for the failure to start the SQL Server.

This video explains the steps to troubleshoot the failures and find the error of a SQL Server startup failure. 

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As always, you can give your feedback as an email to me (bru@learnsqlwithbru.com) or thru comments.

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–Bru Medishetty