RDH: Creating an SQL query from a DAP2 Constraint Expression: Difference between revisions
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(New page: # Each projected variable should appear in the SELECT section. # The name of the Data Source (which is the DAP resource ID) should be used in the FROM section # Each clause should be ...) |
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== DAP Projection == | |||
# Each projected variable should appear in the SELECT section. | # Each projected variable should appear in the SELECT section. | ||
# The name of the Data Source (which is the DAP resource ID) should be used in the FROM section | # The name of the Data Source (which is the DAP resource ID) should be used in the FROM section | ||
== DAP Selection == | |||
# Each clause should be converted (where possible) into a condition in the WHERE section. | # Each clause should be converted (where possible) into a condition in the WHERE section. | ||
# Array sub-setting cannot be encoded in the SQL query and must happen once the row set response has been received. | # Array sub-setting cannot be encoded in the SQL query and must happen once the row set response has been received. | ||
Revision as of 17:12, 5 May 2009
DAP Projection
- Each projected variable should appear in the SELECT section.
- The name of the Data Source (which is the DAP resource ID) should be used in the FROM section
DAP Selection
- Each clause should be converted (where possible) into a condition in the WHERE section.
- 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:
- The use of a limited regular expression type of matching in the CE which could be used to create SQL "LIKE" operators.
- Some kind of a range operation that would map to SQL "BETWEEN" operator.
