Difference Between Update and Alter in SQL

Update statement is used to update existing records in a database. Update is a Data Manipulation Language (DML) statement.

[cc lang=”sql”]
UPDATE tableName
SET column1Name=value1, column2Name=value2, …
WHERE columnXName=someValue
[/cc]

Alter SQL command is used to modify, delete or add a column to an existing table in a database. Alter is a Data Definition Language (DDL) statement.

[cc lang=”sql”]
ALTER TABLE tableName
ADD newColumnName dataTypeOfNewColumn
[/cc]

[cc lang=”sql”]
ALTER TABLE tableName
DROP COLUMN columnName
[/cc]

[cc lang=”sql”]
ALTER TABLE tableName
ALTER COLUMN columnName newDataType
[/cc]

Alter command modifies the database schema, while update statement only modifies records in a database without modifying its structure.

Read more: http://www.differencebetween.com/difference-between-update-and-vs-alter/#ixzz244ZO0N9T