.alter column command
Applies to: ✅ Microsoft Fabric ✅ Azure Data Explorer
Alters the data type of an existing table column.
Warning
When altering the data type of a column, any preexisting data in that column will return a null value in future queries.
After using .alter column, that data cannot be recovered, even by using another command to alter the column type back to a previous value.
For information on how to preserve preexisting data, see Change column type without data loss.
Permissions
You must have at least Table Admin permissions to run this command.
Syntax
.alter column [DatabaseName .] TableName . ColumnName type = ColumnNewType
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| DatabaseName | string |
The name of the database that contains the table. | |
| TableName | string |
✔️ | The name of the table that contains the column to alter. |
| ColumnName | string |
✔️ | The name of the column to alter. |
| ColumnNewType | string |
✔️ | The new data type for the column. |
Example
.alter column ['Table'].['ColumnX'] type=string