RDH: Creating an SQL query from a DAP2 Constraint Expression

DAP Projection

1. Each projected variable should appear as selected columns in the SQL SELECT statement.
2. The name of the Data Source (which is the DAP resource ID) should be used in the FROM section of the SELECT statement.

DAP Selection

1. Each clause should be converted (where possible) into a condition in the WHERE section.
2. Array sub-setting cannot be encoded in the SQL query and must happen once the row set response has been received.

For example, the request:

http://localhost/opendap/rdh/foo?v,u&lat<26&lat>24&lon<-126&lon>-128

would be converted in the SQL query:

SELECT v, u FROM foo WHERE lat<26 AND lat>24 AND lon<-126 AND lon>-128

Additionally we may wish to allow:

1. The use of a limited regular expression type of matching in the CE which could be used to create SQL "LIKE" operators.
2. Some kind of a range operation that would map to SQL "BETWEEN" operator.