How do I concatenate text in a query in sql server?

The following SQL:

SELECT notes + 'SomeText'
FROM NotesTable a 

Give the error:

The data types nvarchar and text are incompatible in the add operator.

The only way would be to convert your text field into an nvarchar field.

Select Cast(notes as nvarchar(4000)) + 'SomeText'
From NotesTable a

Otherwise, I suggest doing the concatenation in your application.

You might want to consider NULL values as well. In your example, if the column notes has a null value, then the resulting value will be NULL. If you want the null values to behave as empty strings (so that the answer comes out 'SomeText'), then use the IsNull function:

Select IsNull(Cast(notes as nvarchar(4000)),'') + 'SomeText' From NotesTable a

If you are using SQL Server 2005 or greater, depending on the size of the data in the Notes field, you may want to consider casting to nvarchar(max) instead of casting to a specific length which could result in string truncation.

Select Cast(notes as nvarchar(max)) + 'SomeText' From NotesTable a