How to DROP COLUMN in SQL Server

How do I safely drop a column in SQL Server?

ALTER TABLE ... DROP COLUMN removes one or more columns from an existing SQL Server table.

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Description

What does ALTER TABLE ... DROP COLUMN do?

The command permanently deletes the specified column(s) and their data from a table. Indexes, defaults, and constraints tied only to those columns are removed automatically.

When should I drop a column?

Drop a column when it is obsolete, replaced by a new attribute, or storing redundant data. Always back up data or verify the column is no longer referenced in code, views, or reports.

How do I drop a single column?

Run ALTER TABLE table_name DROP COLUMN column_name; SQL Server removes the column immediately, so wrap it in a transaction if you may need to roll back.

Can I check first?

Use the IF EXISTS modifier (SQL Server 2016+) to avoid errors when the column is already gone: ALTER TABLE ... DROP COLUMN IF EXISTS.

How do I drop multiple columns?

List them comma-separated: ALTER TABLE Products DROP COLUMN discontinued, legacy_price;

Will dependencies break?

Yes. Any view, stored procedure, or application query that references the column will fail. Search your codebase and run sys.sql_expression_dependencies checks before execution.

Best practices for production?

1) Take a backup. 2) Deploy during low-traffic windows. 3) Wrap in a transaction during smoke tests. 4) Use IF EXISTS for idempotent scripts. 5) Update documentation immediately.

Why How to DROP COLUMN in SQL Server is important

How to DROP COLUMN in SQL Server Example Usage


-- Remove an obsolete DiscountCode column from the Orders table
ALTER TABLE Orders
    DROP COLUMN IF EXISTS DiscountCode;

How to DROP COLUMN in SQL Server Syntax


ALTER TABLE <table_name>
    DROP COLUMN [IF EXISTS] <column_name> [, <column_name2> ...] ;

-- Examples in ecommerce context
-- 1. Remove a single column
ALTER TABLE Orders
    DROP COLUMN IF EXISTS DiscountCode;

-- 2. Remove multiple obsolete columns
ALTER TABLE Products
    DROP COLUMN old_price, supplier_code;

Common Mistakes

Ignoring dependencies. Dropping a column referenced in views or procedures causes runtime errors. Fix by checking sys.sql_expression_dependencies or running sp_depends before the drop.
Skipping backups. Data removal is irreversible once committed. Always export or back up the table, or wrap the ALTER TABLE in an explicit transaction you can roll back.

Frequently Asked Questions (FAQs)

Does DROP COLUMN lock the entire table?

Yes, SQL Server acquires a schema modification lock (SCH-M). Large tables can block concurrent queries. Plan maintenance windows or use partition swapping if possible.