Deleting Records From SQL Table

In this article we will learn how to delete the records from the SQL table using different ways with step by step so beginners and students  can also understand .
Let us consider we have following table names employee in our SQL Server database having following records.
There are following two ways to delete the records from table in SQL Server .
  1. Using Delete Command
  2. Using Truncate command 
  • Delete command
Delete command removes the rows from a table based on the condition that we provide with a WHERE clause.
 key points
  1. DELETE removes rows one at a time and records an entry in the transaction log for each deleted row.
  2. If you want to retain the identity counter, use DELETE instead. If you want to remove table definition and its data, use the DROP TABLE statement.
  3. DELETE Can be used with or without a WHERE clause
  4. DELETE Activates Triggers.
  5. DELETE can be rolled back.
  6. DELETE is DML Command.
  7. DELETE does not reset identity of the table.
Deleting Specific record
To delete the specific record from table then we need to use where clause .
Syntax
delete from TableName where ColumName=value
Example
Lets us consider we are deleting records from above employee table which has id one as
delete from Employee where Id=1
Above query will delete the records from employee table which has id 1 ,after deleting the record then table records will be look like as follows

 Deleting all records
To delete all records from table we need write query without where clause .
Syntax
delete from TableName
Example
delete from Employee
Above query will delete the all records from employee table.
  • Truncate command
Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.
keypoints
  1. TRUNCATE is faster and uses fewer system and transaction log resources than DELETE.
  2. TRUNCATE removes the data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the transaction log.
  3. TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains. The counter used by an identity for new rows is reset to the seed for the column.
  4. You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint. Because TRUNCATE TABLE is not logged, it cannot activate a trigger.
  5. TRUNCATE cannot be rolled back.
  6. TRUNCATE is DDL Command.
  7. TRUNCATE Resets identity of the table.
 Syntax
truncate table TableName
Example
truncate table Employee
Summary
I hope this article is useful for all readers . If you have a suggestion related to this article then please contact me.

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