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Sunday, May 4, 2014
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How to Manipulate Data in Tables using DML Statements: SQL Syntax

8:39 AMSunday, May 4, 2014
After creating a database and the tables, the next step is to store data in the database. As a database developer, you will be required to modify or delete data. You can perform these data manipulations by using the Data Manipulation Language (DML) statement of Transact-SQL.

If the data stored in the database needs to be used by different kinds of client applications, such as mobile devices or Web applications, data should be stored in a format that can be interpreted by any application. For this, SQL Server allows you to store data in the Extensible Mark-up Language (XML) format that can be read by any application.

As a database developer, you need to regularly insert, modify, or delete data, these operations ensure data is up-to-date. For example, in a database that maintains employee details, you need to insert new records in the Employee table, whenever a new employee joins the organization. Similarly, if the details of an employee change, you need to update the existing records. For example, if the salary of any employee increases, you need to update the existing records to reflect this change.

Storing data in a Table

The smallest unit of data that you can add in a table is a row. You can add a row by using the INSERT DML statement. The syntax of the INSERT statement is:
INSERT [INTO]{table_name} [(column_list)]
VALUES {DEFAULT | values_list | select_statement}

Where

  • Table_name specifies the name of the table into which the data is to be inserted. The INTO keyword is optional.
  • Column_list specifies an optional parameter. You can use it when partial data is to be inserted in a table or when the columns to be inserted are defined in a different order.
  • DEFAULT specifies the clause that you can use to insert the default value specified for the column. If a default value is not specified for a column and the column property is specified as NULL, NULL is inserted in the column. If the column does not have any default constraint attached to it and does not allow NULL as the column value, the SQL Server returns an error message and the insert operation is rejected.
  • Value_list specifies the list of values for the table columns that have to be inserted as a row in the table. If a column is to be provided a default value, you can use the DEFAULT keyword instead of a column value. The column value can also be an expression.
  • Select_statement specifies a nested SELECT statement that you can use to insert rows into the table.
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