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ALTER vs. UPDATE: Know the Difference

Shumaila Saeed
By Shumaila Saeed || Updated on February 20, 2024
ALTER modifies the structure of a database table (e.g., adding columns), while UPDATE changes the data within the table (e.g., changing values).
ALTER vs. UPDATE

Key Differences

ALTER is a Data Definition Language (DDL) command in SQL used to modify the structure of a database table, like adding or dropping columns. UPDATE, on the other hand, is a Data Manipulation Language (DML) command used to modify the data within the table, such as updating existing values.
Shumaila Saeed
Shumaila Saeed
Feb 18, 2024
When you use ALTER, you are changing the schema of the database. This includes operations like changing a column's data type or renaming a table. In contrast, using UPDATE involves changing the actual data stored in the database without altering its schema. It's used for tasks like changing a customer's address.
Shumaila Saeed
Shumaila Saeed
Feb 18, 2024
ALTER operations can significantly impact the database structure and may require careful planning in a production environment to avoid data loss. UPDATE operations are more routine and are often used in day-to-day database operations to modify records as data changes.
Shumaila Saeed
Shumaila Saeed
Feb 18, 2024
The scope of ALTER is structural; it does not deal with individual records but with the overall design of the table. UPDATE, however, is concerned with specific records and fields within a table, targeting specific data that needs to be changed.
Shumaila Saeed
Shumaila Saeed
Feb 18, 2024
The impact of ALTER is usually long-term and affects how data is stored and organized in the future. UPDATE impacts the current state of data in the database, reflecting changes in data values but not in the structure.
Shumaila Saeed
Shumaila Saeed
Feb 18, 2024
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Comparison Chart

Command Type

Data Definition Language (DDL)
Data Manipulation Language (DML)
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Feb 18, 2024

Primary Function

Modifies table structure
Modifies data within the table
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Feb 18, 2024

Examples of Use

Adding/dropping columns, changing data types
Changing values of existing records
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Impact on Database

Structural changes
Data content changes
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Usage Scenario

Less frequent, structural adjustments
Regular use for data maintenance
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Shumaila Saeed
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ALTER and UPDATE Definitions

ALTER

A command to make alterations in table design.
ALTER was used to drop a column no longer needed in the database.
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Shumaila Saeed
Jan 23, 2024

UPDATE

Changing specific data entries within table rows.
The UPDATE command corrected the pricing errors in the product table.
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Shumaila Saeed
Jan 23, 2024

ALTER

To modify the structure of a database table.
The database administrator used ALTER to add a new column to the table.
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Shumaila Saeed
Jan 23, 2024

UPDATE

SQL command for updating field values in a table.
UPDATE was necessary to revise the status of pending orders.
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Shumaila Saeed
Jan 23, 2024

ALTER

SQL command used for making structural changes in a database.
ALTER TABLE was necessary to rename the outdated column name.
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Shumaila Saeed
Jan 23, 2024
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UPDATE

Refreshing data in a table without altering its structure.
The UPDATE statement was used to synchronize the latest user data.
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Shumaila Saeed
Jan 23, 2024

ALTER

Adjusting database schema, like adding constraints.
He used ALTER to add a foreign key constraint to the table.
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Jan 23, 2024

UPDATE

To modify existing data in a database table.
She used UPDATE to change the customer's address in the records.
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Shumaila Saeed
Jan 23, 2024

ALTER

Changing the characteristics of a table element.
They had to ALTER the data type of the column to accommodate larger values.
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Shumaila Saeed
Jan 23, 2024

UPDATE

Applying changes to specific data in a database.
He executed an UPDATE to adjust the inventory quantities.
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Shumaila Saeed
Jan 23, 2024

Repeatedly Asked Queries

Can ALTER change data in a table?

No, it changes the table's structure, not the data.
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Shumaila Saeed
Feb 18, 2024

Does ALTER affect existing data?

It can, especially if columns are dropped or data types changed.
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Shumaila Saeed
Feb 18, 2024

Can UPDATE change a table's design?

No, it only modifies the contents of existing columns.
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Shumaila Saeed
Feb 18, 2024

What is a common use of ALTER?

Adding new columns to a table.
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Shumaila Saeed
Feb 18, 2024

What does ALTER do in SQL?

It modifies the structure of a database table.
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Feb 18, 2024

Is ALTER reversible?

Sometimes, but not always without data loss.
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What is the purpose of UPDATE in a database?

To change existing data within a table.
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What is a typical scenario for using UPDATE?

Changing values in a customer's record.
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Shumaila Saeed
Feb 18, 2024

Is UPDATE used for adding columns?

No, UPDATE is for modifying data, not structure.
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Feb 18, 2024

Does ALTER require careful planning?

Yes, due to its impact on database structure.
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Shumaila Saeed
Feb 18, 2024

Can UPDATE be used on multiple rows?

Yes, it can update one or more rows at a time.
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Feb 18, 2024

Are permissions important for using ALTER?

Yes, it usually requires higher permissions due to its impact.
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Feb 18, 2024

Is ALTER frequently used?

Less so than UPDATE, as it involves structural changes.
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Shumaila Saeed
Feb 18, 2024

How often is UPDATE used?

Regularly, for routine data modifications.
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Feb 18, 2024

Do you need special permissions to use UPDATE?

Yes, but typically less than for ALTER commands.
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Shumaila Saeed
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Is UPDATE complex to execute?

It's relatively straightforward for those familiar with SQL.
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Shumaila Saeed
Feb 18, 2024

What's a risk with ALTER?

Incorrect use can lead to data loss or corruption.
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Shumaila Saeed
Feb 18, 2024

Is UPDATE risky?

Less so, but incorrect updates can lead to incorrect data.
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Can UPDATE be undone?

Yes, if the previous data values are known.
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Can ALTER be used to rename a table?

Yes, it can change table names.
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Shumaila Saeed
Feb 18, 2024

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About Author
Shumaila Saeed
Written by
Shumaila Saeed
Shumaila Saeed, an expert content creator with 6 years of experience, specializes in distilling complex topics into easily digestible comparisons, shining a light on the nuances that both inform and educate readers with clarity and accuracy.

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