If you want to create an expression for the Asset Description field to return the records where the field contains the value This is a test, the expression would be:
WHERE [Asset].[ASSET DESC CHR] LIKE 'This is a test'
...where This is a test is within single quotation marks because it is the stored value that you want to use to limit the query results.
Note that text fields are stored in the database differently than character fields and are, therefore, handled differently. One difference is that you cannot use the = operator with text fields. Instead, you must use the like operator. When creating text field expressions, be sure to specify the like operator.
Note: When you are using an Oracle schema, the value is case sensitive by default. This means, for example, that if you enter WHERE [Asset].[ASSET DESC CHR] LIKE 'This is a test' in a field where values are stored in the database as This is a test, the query will not return any results.