ALTER vs. UPDATE: Know the Difference
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).
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
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
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
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
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
Feb 18, 2024
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Comparison Chart
Command Type
Data Definition Language (DDL)
Data Manipulation Language (DML)
Shumaila Saeed
Feb 18, 2024
Examples of Use
Adding/dropping columns, changing data types
Changing values of existing records
Shumaila Saeed
Feb 18, 2024
Usage Scenario
Less frequent, structural adjustments
Regular use for data maintenance
Shumaila Saeed
Feb 18, 2024
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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.
Shumaila Saeed
Jan 23, 2024
UPDATE
Changing specific data entries within table rows.
The UPDATE command corrected the pricing errors in the product table.
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.
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.
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.
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.
Shumaila Saeed
Jan 23, 2024
ALTER
Adjusting database schema, like adding constraints.
He used ALTER to add a foreign key constraint to the table.
Shumaila Saeed
Jan 23, 2024
UPDATE
To modify existing data in a database table.
She used UPDATE to change the customer's address in the records.
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.
Shumaila Saeed
Jan 23, 2024
UPDATE
Applying changes to specific data in a database.
He executed an UPDATE to adjust the inventory quantities.
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.
Shumaila Saeed
Feb 18, 2024
Does ALTER affect existing data?
It can, especially if columns are dropped or data types changed.
Shumaila Saeed
Feb 18, 2024
Can UPDATE change a table's design?
No, it only modifies the contents of existing columns.
Shumaila Saeed
Feb 18, 2024
What is the purpose of UPDATE in a database?
To change existing data within a table.
Shumaila Saeed
Feb 18, 2024
What is a typical scenario for using UPDATE?
Changing values in a customer's record.
Shumaila Saeed
Feb 18, 2024
Is UPDATE used for adding columns?
No, UPDATE is for modifying data, not structure.
Shumaila Saeed
Feb 18, 2024
Does ALTER require careful planning?
Yes, due to its impact on database structure.
Shumaila Saeed
Feb 18, 2024
Can UPDATE be used on multiple rows?
Yes, it can update one or more rows at a time.
Shumaila Saeed
Feb 18, 2024
Are permissions important for using ALTER?
Yes, it usually requires higher permissions due to its impact.
Shumaila Saeed
Feb 18, 2024
Is ALTER frequently used?
Less so than UPDATE, as it involves structural changes.
Shumaila Saeed
Feb 18, 2024
Do you need special permissions to use UPDATE?
Yes, but typically less than for ALTER commands.
Shumaila Saeed
Feb 18, 2024
Is UPDATE complex to execute?
It's relatively straightforward for those familiar with SQL.
Shumaila Saeed
Feb 18, 2024
What's a risk with ALTER?
Incorrect use can lead to data loss or corruption.
Shumaila Saeed
Feb 18, 2024
Is UPDATE risky?
Less so, but incorrect updates can lead to incorrect data.
Shumaila Saeed
Feb 18, 2024
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About Author
Written by
Shumaila SaeedShumaila 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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