RDH: Creating an SQL query from a DAP2 Constraint Expression: Difference between revisions
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== DAP Projection == | == DAP Projection == | ||
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Additionally we may wish to allow: | 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. | # The use of a limited regular expression type of matching in the CE which could be used to create [http://www.w3schools.com/sql/sql_like.asp SQL "LIKE" operators]. | ||
# Some kind of a range operation that would map to SQL "BETWEEN" operator. | # Some kind of a range operation that would map to [http://www.w3schools.com/sql/sql_between.asp SQL "BETWEEN" operator]. | ||
Revision as of 17:13, 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.
