Programming Groovy 2

9.5 Using DataSet

In Section 9.3, ​Database Select​, we saw how to process the results set obtained from executing a ​SELECT​ query. If we want to receive only a filtered set of rows, such as only cities with temperature values below 32, we can set up the query accordingly. Alternatively, we can receive the result as a ​groovy.sql.DataSet​ to filter data. Let’s examine this further.

The ​dataSet​ method of the ​Sql​ class takes a table’s name and returns a virtual proxy—it does not fetch the actual rows until we iterate. We can then iterate over the rows using the ​each​ method of the ​DataSet​ (like the ​eachRow​ method of ​Sql​). In the following code, however, we’ll use the ​findAll​ method to filter the results to obtain only cities with ...