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SQL Add Column

SQL Create Index

SQL Constraints

The ALTER TABLE command is used to manage columns in a table.

To add a column use the ADD option.

To change a column use the ALTER option.

To remove a column use the DROP option.

Example

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This example adds an Email column to the Supplier table.

ALTER TABLE Supplier
  ADD Email NVARCHAR(60)

Syntax

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Syntax to add a column.

  ALTER TABLE table-name
    ADD column-name data-type

Syntax to change a column. Effectively, this changes the data type.

  ALTER TABLE table-name
    ALTER COLUMN column-name data-type

Syntax to remove (drop) a column.

  ALTER TABLE table-name
    DROP COLUMN column-name

More Examples

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ALTER TABLE. Change COLUMN

SUPPLIER
Id
CompanyName
ContactName
City
Country
Phone
Fax

Problem: Increase the size of CompanyName to 100 characters in the Supplier table.

ALTER TABLE Supplier
  ALTER COLUMN CompanyName NVARCHAR(100)

Result: Column altered

ALTER TABLE. Drop COLUMN

SUPPLIER
Id
CompanyName
ContactName
City
Country
Phone
Fax

Problem: Remove the Fax column from the Supplier table.

ALTER TABLE Supplier
  DROP COLUMN Fax

Result: Column dropped

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