Casting Individual Fields of a Row Type

If an operation on a field of a row type requires an explicit cast, you can explicitly cast the individual field value without consideration of the row type with which the field is associated. The following statement uses an explicit cast on the field value to handle the conversion:

SELECT col1 from tab1, tab2 WHERE col1.b = col2.b::FLOAT::d_float

If an operation on a field of a row type requires an implicit cast, you can simply specify the appropriate field value and the database server handles the conversion automatically. In the following statement, which compares field values of different data types, a built-in cast automatically converts between INT and FLOAT values:

SELECT col1 from tab1, tab2 WHERE col1.a = col2.b