SQL ALTER

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ALTER TABLE statement

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

SQL ALTER TABLE syntax

To add columns to the table, please use the following syntax:

To delete a column in a table, use the following syntax (please note that some database systems do not allow this method of deleting columns in a database table):

To change the data type of a column in a table, use the following syntax:

SQL Server/MS Access:

My SQL/Oracle:

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##SQL ALTER TABLE example

Please see the "Persons" table:

P_IdLastNameFirstNameAddressCity1HansenOlaTimoteivn 10Sandnes2SvendsonToveBorgvn 23Sandnes3PettersenKariStorgt 20StavangerNow, we want to add a column called "DateOfBirth" to the "Persons" table.

We use the following SQL statement:

Please note that the type of the new column "DateOfBirth" It is date, which can store the date. The data type specifies the type of data that can be stored in the column. To learn about the data types available in MS Access, MySQL and SQL Server, visit our complete

Data Types Reference.

Now, the "Persons" table will look like this:

P_IdLastNameFirstNameAddressCityDateOfBirth##1##2SvendsonToveBorgvn 23SandnesPettersen

Hansen	Ola	Timoteivn 10	Sandnes
					##3
Kari	Storgt 20	Stavanger			Change Data Type Example Now, we want to change the data type of the "DateOfBirth" column in the "Persons" table. We use the following SQL statement: ALTER TABLE Persons ALTER COLUMN DateOfBirth year Please note that now the "DateOfBirth" column The type is year, which can store the year in 2-digit or 4-digit format. DROP COLUMN Example Next, we want to delete the "DateOfBirth" column in the "Person" table. We use the following SQL statement: ALTER TABLE Persons DROP COLUMN DateOfBirth Now, the "Persons" table will look like this : P_Id LastName FirstName Address City 1 Hansen Ola Timoteivn 10 Sandnes 2 Svendson Tove Borgvn 23 Sandnes 3 Pettersen Kari Storgt 20 Stavanger ← SQL DROP SQL AUTO INCREMENT → submit php.cn HomeCourseArticleQ&ADictionaryManualDownloadsearch APPDownload