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Power BI Refresh Error:
4902

What does this error mean?

An ALTER TABLE statement references a column, constraint, or index that does not exist in the table.

Common causes

  • 1A migration script attempts to drop a column that was already removed in a previous migration
  • 2A column name is misspelled in the ALTER TABLE statement
  • 3The script targets the wrong table or schema

How to fix it

  1. 1Step 1: Check current table columns: SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'YourTable' ORDER BY ORDINAL_POSITION;
  2. 2Step 2: Use conditional ALTER: IF COL_LENGTH('dbo.YourTable', 'old_column') IS NOT NULL ALTER TABLE [dbo].[YourTable] DROP COLUMN [old_column];
  3. 3Step 3: Ensure the migration script runs in order and is not run twice — use a migration framework like Flyway or DbUp to track script execution.

Frequently asked questions

How do I check if a column exists before dropping it?

Use COL_LENGTH: IF COL_LENGTH('dbo.YourTable', 'ColumnName') IS NOT NULL ALTER TABLE [dbo].[YourTable] DROP COLUMN [ColumnName]; — COL_LENGTH returns NULL if the column does not exist.

Does dbt run ALTER TABLE statements?

dbt does not run ALTER TABLE by default. It uses DROP and CREATE (or MERGE for incremental models). However, some dbt macros or post-hooks may include ALTER statements for constraint management.

What is the idiomatic SQL Server way to check constraint existence?

For constraints: IF EXISTS (SELECT 1 FROM sys.objects WHERE name = 'CK_MyConstraint' AND parent_object_id = OBJECT_ID('dbo.MyTable')) ALTER TABLE [dbo].[MyTable] DROP CONSTRAINT [CK_MyConstraint];

Official documentation: https://learn.microsoft.com/en-us/sql/relational-databases/errors-events/database-engine-events-and-errors

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